John Locke: The Father of Empiricism and Liberalism

First published Sun Sep 2, 2001; substantive revision Thu Jul 7, 2022

John Locke (1632–1704) stands as a towering figure in Western philosophy, an English thinker whose profound insights shaped not only the trajectory of philosophical thought but also the course of political and social development in the modern era. An Oxford academic and medical researcher by training, Locke’s intellectual breadth extended across epistemology, political theory, education, and religious toleration, making him a multifaceted contributor to the Enlightenment. His seminal work, An Essay Concerning Human Understanding (1689), is a cornerstone of modern empiricism, meticulously exploring the limits of human knowledge and laying the groundwork for subsequent empirical traditions. In politics, Locke is celebrated for The Second Treatise of Government, a powerful articulation of natural rights, the social contract, and the sovereignty of the people that profoundly influenced the American and French Revolutions. His Letter Concerning Toleration further cemented his legacy as a champion of individual liberty and the separation of church and state.

Locke’s philosophy is fundamentally characterized by a deep-seated opposition to authoritarianism in all its forms, whether intellectual, political, or religious. He championed the individual’s right to reason and independent thought, arguing against blind acceptance of authority and superstition. Locke urged individuals to base their beliefs on evidence and reason, a principle that extended to his views on governance and institutions. He advocated for the separation of powers and the limitation of governmental authority, emphasizing the importance of individual freedom and the consent of the governed. For Locke, the pursuit of truth through reason and the establishment of just institutions were essential for human flourishing, aligning with natural law and fulfilling humanity’s divine purpose. His enduring influence stems from his powerful defense of individual liberty, reason, and limited government – ideas that continue to resonate deeply in contemporary discussions of politics, knowledge, and human rights.

A portrait of John Locke, the influential 17th-century English philosopher, highlighting his intellectual contributions to empiricism and liberalism.

1. The Life and Times of John Locke: A Historical Context

John Locke, born in 1632 and passing away in 1704, emerged as one of the most significant European philosophers as the seventeenth century drew to a close. His life unfolded against the backdrop of a tumultuous period in English history, a century marked by dramatic political and intellectual shifts. This era witnessed intense conflicts between the Crown and Parliament, intertwined with religious strife between Protestants, Anglicans, and Catholics, culminating in the English Civil War in the 1640s. The execution of Charles I ushered in a radical experiment in governance, including the abolition of the monarchy, the House of Lords, and the Anglican Church, and the rise of Oliver Cromwell’s Protectorate in the 1650s.

The Protectorate’s collapse after Cromwell’s death paved the way for the Restoration of Charles II in 1660, reinstating the monarchy, the House of Lords, and the Anglican Church. However, this period, lasting until 1688, was not one of stability. Tensions persisted between the King and Parliament, fueled by ongoing debates about religious toleration for both Protestant dissenters and Catholics. This era of unrest concluded with the Glorious Revolution of 1688, which saw James II deposed and replaced by William of Orange and his wife Mary. Locke’s final years were spent during the consolidation of power by William and Mary and the commencement of William’s efforts to counter the hegemonic ambitions of Louis XIV’s France, a conflict that would eventually lead to the military triumphs of John Churchill, the Duke of Marlborough.

1.1 Early Life and Education: From Puritan Roots to Oxford Scholar

John Locke‘s origins were modest, born in Wrington to Puritan parents. His father, a country lawyer, served on the Parliamentarian side during the early phases of the English Civil War. Crucially, his father’s commander, Alexander Popham, became the local Member of Parliament and provided the patronage that enabled the young John Locke to receive an exceptional education. In 1647, Locke entered Westminster School in London, a prestigious institution that prepared him for higher learning.

In the autumn of 1652, at the age of twenty, Locke matriculated at Christ Church, Oxford, the most esteemed college within the preeminent English university. Oxford’s educational system at the time remained rooted in medieval traditions, heavily emphasizing Aristotelian philosophy. Like Thomas Hobbes before him, Locke found the Aristotelian curriculum largely unproductive. However, Oxford was also experiencing intellectual ferment. The burgeoning “new experimental philosophy” was taking hold, spearheaded by figures like John Wilkins, Cromwell’s brother-in-law and the Warden of Wadham College. Wilkins’ circle formed the nucleus of what would become the English Royal Society. Emerging from informal gatherings and discussions, the Society formally established itself in London after the Restoration in the 1660s, receiving royal charters from Charles II. The Royal Society distinguished itself from the university’s scholastic Aristotelianism, advocating for the study of nature through observation and experiment rather than reliance on classical texts.

Many of Wilkins’ associates were deeply involved in medicine, favoring observation-based practices over traditional textual authorities. Francis Bacon’s emphasis on systematic experimentation and the methodical collection of empirical data to derive generalizations resonated strongly with this group. Richard Lower, a friend of Locke‘s from Westminster, introduced him to medicine and the experimental philosophy championed by the Wadham virtuosi.

Locke earned his Bachelor of Arts degree in February 1656. His academic career at Oxford extended beyond his undergraduate studies. In June 1658, he obtained his Master of Arts degree and was elected a Senior Student at Christ Church College, a position comparable to a Fellowship at other colleges, though not permanent. Locke was at a crossroads regarding his future profession. He was appointed Lecturer in Greek at Christ Church in December 1660 and Lecturer in Rhetoric in 1663. However, Christ Church statutes stipulated that the majority of senior studentships were reserved for men in holy orders or pursuing ordination, with only a few exceptions for medicine, law, and moral philosophy. This created a strong incentive for Locke to enter the clergy. Yet, since his graduation, Locke had been increasingly drawn to the study of medicine. Ultimately, Locke decided to pursue a career as a physician.

Following the Restoration of Charles II, John Wilkins left Oxford. Robert Boyle became the leading figure in the Oxford scientific community and Locke’s scientific mentor. Boyle, with the assistance of Robert Hooke, constructed an air pump that led to Boyle’s Law and invented a barometer for weather forecasting. Boyle’s work with the air pump sparked a debate with Thomas Hobbes, whose micro-corpuscular theory was incompatible with Boyle’s explanations of the air pump’s operation. This intellectual clash lasted for a decade. Boyle’s most significant influence, however, was as a theorist. He was a mechanical philosopher who posited that the world could be reduced to matter in motion, although he lacked a micro-corpuscular explanation of air itself.

Locke encountered Boyle’s work before engaging with René Descartes. Upon reading Descartes, Locke recognized the French philosopher as offering a viable alternative to the sterile Aristotelianism he had experienced at Oxford. In writing An Essay Concerning Human Understanding, Locke adopted Descartes’ “way of ideas,” transforming it into an integral component of his own philosophical framework. Despite his admiration for Descartes, Locke’s association with the Oxford scientists fostered a critical perspective toward the rationalist elements in Descartes’ philosophy.

In his Epistle to the Reader in An Essay Concerning Human Understanding, Locke humbly describes his role in the intellectual landscape:

The commonwealth of learning is not at this time without master-builders, whose mighty designs, in advancing the sciences, will leave lasting monuments to the admiration of posterity: but everyone must not hope to be a Boyle or a Sydenham; and in an age that produces such masters as the great Huygenius and the incomparable Mr. Newton, with some others of that strain, it is ambition enough to be employed as an under-labourer in clearing the ground a little, and removing some of the rubbish that lies in the way to knowledge …. (N: 9–10; all quotations are from the Nidditch edition of An Essay Concerning Human Understanding [N])

Locke was personally acquainted with Boyle, Sydenham, Huygens, and Newton and deeply familiar with their groundbreaking work. Locke, Boyle, and Newton were all either founding or early members of the English Royal Society. From Boyle, Locke learned about atomism (or the corpuscular hypothesis), and he adopted the language of primary and secondary qualities from Boyle’s The Origin of Forms and Qualities. Thomas Sydenham, an English physician with whom Locke conducted medical research, advocated for careful observation of diseases, rejecting speculation about underlying causes. Boyle and Newton both conducted research on colors that did not rely on micro-corpuscular explanations. While in exile in Holland, Locke studied Newton’s Principia Mathematica Philosophiae Naturalis, consulting Huygens to verify its mathematical soundness. Locke and Newton became friends after Locke’s return from Holland in 1688. Locke’s self-description as an “under-laborer” may reflect not only literary modesty but also a contrast between the significant scientific discoveries of his contemporaries and his own project of critiquing Aristotelian, Scholastic, and to some extent, Cartesian philosophies. However, as Jolley (1999: 15–17) points out, this image of an under-laborer does not fully capture the scope of Locke’s project. While corpuscular philosophy and Newton’s discoveries profoundly influenced Locke, his Introduction to the Essay references the Baconian program of producing natural histories when he describes his own approach:

It shall suffice to my present Purpose, to consider the discerning Faculties of a Man, as they are employ’d about the Objects, which they have to do with: and I shall imagine that I have not wholly misimploy’d my self in the Thoughts I shall have on this Occasion, if in this Historical, Plain Method, I can give any Account of the Ways, whereby our Understanding comes to attain those Notions of Things, and can set down any Measure of the Certainty of our Knowledge…. (I.1.2, N: 43–4—the three numbers, are book, chapter and section numbers respectively, followed by the page number in the Nidditch edition)

The “Historical, Plain Method” appears to denote a genetic account of how we acquire our ideas, intended to reveal the degree of certainty inherent in the knowledge derived from these ideas. Locke‘s direct involvement in the scientific movement was largely through his informal medical studies. Dr. David Thomas, a close friend and collaborator, shared a laboratory with Locke in Oxford, which likely functioned as a pharmacy. In 1666, Lord Ashley, a prominent and wealthy figure in England, visited Oxford seeking medicinal waters and requested Dr. Thomas to provide them. When Thomas was unavailable, he delegated the task to Locke. This chance encounter led Ashley to invite Locke to London as his personal physician. In 1667, Locke moved to London, becoming not only Lord Ashley’s physician but also his secretary, researcher, political advisor, and close friend, placing Locke at the heart of English politics during the 1670s and 1680s.

1.2 Association with Lord Shaftesbury: Politics and Philosophy Converge (1666-1688)

Upon joining Lord Ashley’s household at Exeter House in 1668, John Locke‘s primary role was that of Ashley’s physician. Locke’s medical expertise proved crucial when he organized a successful operation on Ashley, a procedure meticulously documented for the 17th century. Locke consulted physicians across England to determine best practices and emphasized hygiene, ultimately saving his patron’s life and potentially altering the course of English history.

Beyond medicine, Locke undertook various roles for Ashley. He served as Secretary of the Board of Trade and Plantations and Secretary to the Lords Proprietors of the Carolinas. Lord Ashley championed the view that England’s prosperity depended on trade and that colonies could significantly contribute to this endeavor. Ashley persuaded Charles II to establish the Board of Trade and Plantations to gather information on trade and colonies, and Locke was appointed its secretary. In this capacity, Locke became a central hub for information from around the world, providing the English government with crucial data on trade and colonial affairs. Ashley also pursued colonial ventures in the Carolinas. As secretary to the Lords Proprietors, Locke participated in drafting the fundamental constitution for the Carolinas, although the extent of his contribution remains debated.

John Locke‘s involvement with Shaftesbury extended to broader public policy issues beyond trade and colonies. During an English monetary crisis involving currency devaluation and coin clipping, Locke authored papers for Lord Ashley on economic matters, including the coinage crisis.

Even amidst his political and administrative duties in London, Locke continued his philosophical pursuits. He recounted the genesis of An Essay Concerning Human Understanding:

Were it fit to trouble thee with the history of this Essay, I should tell thee, that five or six friends meeting at my chamber, and discoursing on a subject very remote from this, found themselves quickly at a stand, by the difficulties that rose on every side. After we had awhile puzzled ourselves, without coming any nearer a resolution of those doubts which perplexed us, it came into my thoughts that we took a wrong course; and that before we set ourselves upon inquiries of that nature, it was necessary to examine our own abilities, and see what objects our understandings were, or were not, fitted to deal with. This I proposed to the company, who all readily assented; and thereupon it was agreed that this should be our first inquiry. Some hasty and undigested thoughts, on a subject I had never before considered, which I set down against our next meeting, gave the first entrance into this Discourse; which having been thus begun by chance, was continued by intreaty; written by incoherent parcels; and after long intervals of neglect, resumed again, as my humour or occasions permitted; and at last, in a retirement where an attendance on my health gave me leisure, it was brought into that order thou now seest it. (Epistle to the Reader, N: 7)

James Tyrrell, one of Locke’s friends present at that meeting, recalled the discussion centered on the principles of morality and revealed religion (Cranston 1957: 140–1). This intellectual gathering marked the inception of the project that would occupy Locke intermittently over the next two decades.

In 1674, after Shaftesbury left government, Locke returned to Oxford, earning a Bachelor of Medicine degree and a license to practice medicine, before traveling to France (Cranston 1957: 160). During his time in France, Locke journeyed from Calais to Paris, Lyons, and Montpellier, spending fifteen months primarily studying Protestantism in France. The Edict of Nantes, enacted by Henry IV in 1598, was in effect, granting a degree of religious toleration in France. However, Louis XIV revoked the Edict in 1685, leading to the persecution of French Protestants, with mass killings and approximately 400,000 fleeing into exile.

While Locke was in France, Shaftesbury’s political fortunes fluctuated. In 1676, Shaftesbury was imprisoned in the Tower of London for a year. In 1678, following the mysterious murder of a London judge, informants, notably Titus Oates, emerged, alleging a Catholic plot to assassinate the King and install his brother on the throne. This fueled widespread anti-Catholic hysteria. Although Shaftesbury did not invent the conspiracy theory nor instigate Oates, he skillfully exploited the situation to benefit his political faction. Amidst the public turmoil caused by these sensational revelations, Shaftesbury built a robust party network, exerted significant influence over elections, and gained a substantial parliamentary majority. His strategy was to pass an Exclusion Bill to prevent Charles II’s openly Catholic brother from ascending to the throne. Despite passing in the Commons, the Exclusion Bill was defeated in the House of Lords due to the King’s strong opposition. As public fear of the Popish Plot subsided, Shaftesbury lost support and momentum. Shaftesbury was arrested again on July 21, 1681, and imprisoned in the Tower. He was tried for treason on fabricated charges but acquitted in November by a London grand jury composed of his supporters.

At this point, some Country Party leaders began plotting an armed rebellion, intending to assassinate Charles and his brother on their return to London from Newmarket races. However, the prospects for such an uprising were less favorable than the plotters believed, as memories of the Civil War’s chaos remained vivid. Eventually, Shaftesbury, moving between safe houses, fled to Holland in November 1682, where he died in January 1683. Locke remained in England until the Rye House Plot, named after the location where the assassination was planned, was uncovered in June 1683. Locke left for the West Country to settle his affairs the week the plot was revealed and by September was in exile in Holland.

During his exile, Locke completed An Essay Concerning Human Understanding and published a fifty-page French abstract of it. This abstract served as the primary source of information about the Essay for continental intellectuals until Pierre Coste’s French translation appeared in 1704. He also wrote and published Epistola de Tolerentia in Latin. Richard Ashcraft, in Revolutionary Politics and Locke’s Two Treatises of Government (1986), suggests that Locke was not only finishing the Essay and tending to his health in Holland but was also deeply involved with exiled English revolutionaries. The English government was highly concerned about this group and attempted to extradite several members, including Locke, back to England. Locke’s studentship at Oxford was revoked in absentia. Simultaneously, English intelligence infiltrated the rebel group in Holland, effectively disrupting their plans, at least temporarily. While Locke was in exile, Charles II died on February 6, 1685, and was succeeded by his brother, James II of England. Shortly after, the exiled rebels in Holland, led by the Duke of Monmouth, launched a military attempt to overthrow James II in England. The revolt was quickly suppressed, and Monmouth was captured and executed (Ashcraft 1986). Roger Woolhouse’s Locke: A Biography (2007) provides a detailed and cautious examination of the evidence regarding Locke’s involvement with the English rebels in exile.

Ultimately, the revolutionaries were successful. James II alienated much of his support, and William of Orange was invited to bring a Dutch force to England. Upon William’s army landing, James II, recognizing the futility of resistance, fled to France. This event, known as the Glorious Revolution of 1688, marked a pivotal moment in English history, decisively shifting the balance of power from the monarchy to Parliament. Locke returned to England in February 1689, following the revolution.

1.3 Final Years: Intellectual Output and Public Service (1689-1704)

Following his return from exile, John Locke published An Essay Concerning Human Understanding and Two Treatises of Government. Additionally, Popple’s English translation of Locke’s A Letter Concerning Toleration was also published. Notably, both Two Treatises and A Letter Concerning Toleration were published anonymously. Locke took up residence in the countryside at Oates in Essex, the home of Sir Francis and Lady Masham (Damaris Cudworth). Locke had met Damaris Cudworth in 1682 and developed a close intellectual and romantic relationship with her. She was the daughter of Ralph Cudworth, the Cambridge Platonist, and a philosopher in her own right. After Locke went into exile in Holland in 1683, she married Sir Francis Masham. Locke and Lady Masham remained close friends and intellectual companions for the rest of Locke’s life. In his final years, Locke oversaw four more editions of the Essay and engaged in intellectual debates concerning the Essay, most notably in a series of published letters with Edward Stillingfleet, the Bishop of Worcester. Similarly, Locke defended A Letter Concerning Toleration against various critiques. He also wrote The Reasonableness of Christianity and Some Thoughts on Education during this period.

Locke continued to be involved in public affairs. In 1696, the Board of Trade was re-established. Locke played a crucial role in its revival and served as its most influential member until 1700. The new Board of Trade possessed administrative powers and addressed a wide array of issues, from the Irish wool trade and suppressing piracy to poverty in England and colonial governance. Peter Laslett described it as “the body which administered the United States before the American Revolution” (Laslett 1954 [1990: 127]). During these last eight years of his life, Locke suffered increasingly from asthma, tolerating London’s air only during the warmer months. Locke’s dedication to the Board of Trade stemmed from a strong sense of patriotic duty. After retiring from the Board in 1700, Locke remained in retirement at Oates until his death on Sunday, October 28, 1704.

2. Exploring the Boundaries of Human Understanding: Locke’s Epistemology

John Locke is often regarded as the foundational figure of British empiricism, though the claims of Bacon and Hobbes are also recognized. This reputation is primarily based on his magnum opus, An Essay Concerning Human Understanding. Locke elucidates his project in several passages, with a central objective being to delineate the limits of human understanding. Locke states:

For I thought that the first Step towards satisfying the several Enquiries, the Mind of Man was apt to run into, was, to take a Survey of our own Understandings, examine our own Powers, and see to what Things they were adapted. Till that was done, I suspected that we began at the wrong end, and in vain sought for Satisfaction in a quiet and secure Possession of Truths, that most concern’d us whilst we let loose our Thoughts into the vast Ocean of Being, as if all the boundless Extent, were the natural and undoubted Possessions of our Understandings, wherein there was nothing that escaped its Decisions, or that escaped its Comprehension. Thus Men, extending their Enquiries beyond their Capacities, and letting their Thoughts wander into those depths where they can find no sure Footing; ’tis no Wonder, that they raise Questions and multiply Disputes, which never coming to any clear Resolution, are proper to only continue and increase their Doubts, and to confirm them at last in a perfect Skepticism. Wheras were the Capacities of our Understanding well considered, the Extent of our Knowledge once discovered, and the Horizon found, which sets the boundary between the enlightened and the dark Parts of Things; between what is and what is not comprehensible by us, Men would perhaps with less scruple acquiesce in the avow’d Ignorance of the one; and employ their Thoughts and Discourse, with more Advantage and Satisfaction in the other. (I.1.7, N: 47)

While earlier philosophers had suggested the value of determining the limits of understanding, Locke undertook this project with unprecedented thoroughness. In the Essay‘s four books, Locke investigates the sources and nature of human knowledge. Book I refutes the notion of innate knowledge, aligning him with Berkeley and Hume and distinguishing him from Descartes and Leibniz. Locke posits that at birth, the human mind is essentially a blank slate upon which experience inscribes itself. Book II argues that ideas are the fundamental materials of knowledge, and all ideas originate from experience. Locke defines “idea” broadly as “…whatsoever is the Object of the Understanding, when a man thinks” (I.1.8, N: 47). Experience is twofold: sensation and reflection. Sensation provides information about the external world, while reflection is an internal sense that makes us aware of our own mental operations. Some ideas derive solely from sensation, others solely from reflection, and some from both.

Locke proposes an atomic or corpuscular theory of ideas. This suggests an analogy between the combination of atoms or corpuscles to form physical objects and the combination of ideas. Ideas are categorized as simple or complex. We cannot create simple ideas; they are derived solely from experience, making the mind passive in this respect. However, once the mind possesses a store of simple ideas, it can actively combine them into complex ideas of various types. Locke identifies complex ideas as either ideas of substances or ideas of modes. Substances are independent existences, encompassing beings like God, angels, humans, animals, plants, and manufactured objects. Modes are dependent existences, including mathematical, moral, religious, political, and cultural concepts. The mind also relates ideas, whether simple or complex, by placing them side-by-side to perceive their relationships without uniting them, forming ideas of relations (II.12.1, N: 163). Finally, abstraction allows the mind to create general ideas from particulars by omitting specific details of time and place, broadening an idea’s application beyond individual instances. Faculties like memory enable the storage of ideas.

Having outlined the mechanisms by which simple and complex ideas of substances, modes, relations, and other categories are derived from sensation and reflection, Locke details the origins of specific ideas, including solidity, number, space, time, power, identity, and moral relations. Several of these are particularly significant. His chapter on power delves into free will and voluntary action (see the entry on Locke on freedom). Locke also made notable contributions to the philosophy of mind, suggesting, for example, that God could equally grant matter, properly organized, the powers of perception and thought, as he could attach these powers to an immaterial substance joined with matter. His account of personal identity in Book II, Chapter xxvii, was revolutionary (See the entry on Locke on personal identity). These topics and related issues are further explored in the supplementary document: Some Interesting Issues in Locke’s Philosophy of Mind

The following discussion focuses on key aspects of Locke’s account of physical objects. (See also the entry Locke’s philosophy of science, which delves into topics related to Locke’s account of physical objects that are important but beyond the scope of this general overview, including Locke on knowledge in natural philosophy, the limitations of corpuscular philosophy, and his relationship with Newton.)

Locke presents a view of physical objects grounded in mechanical philosophy and the corpuscular hypothesis. Mechanical philosophy explained material phenomena through matter in motion and the impact of bodies on each other, viewing matter as passive and rejecting Aristotelian “occult qualities” and “action at a distance”. Robert Boyle’s corpuscularianism proposed that the material world is composed of particles. Some corpuscularians believed particles were further divisible and the universe was filled with matter, lacking void space. Atomists, conversely, held that particles were indivisible atoms moving in void space. Locke was an atomist.

Atoms possess properties such as extension, solidity, shape, and motion or rest. They combine to form familiar substances and physical objects like gold, wood, animals, plants, furniture, etc. These familiar objects also exhibit properties: extension, solidity, shape, motion, and rest, as well as properties like color, smell, and taste that arise from their interaction with perceivers. This distinction between property types dates back to Greek atomists and was elaborated by Galileo, Descartes, and Boyle.

Locke addresses this distinction in Essay Book II, Chapter 8, using Boyle’s terminology to categorize properties as primary and secondary qualities. This distinction is central to both branches of 17th and early 18th-century mechanical philosophy. Both Cartesian plenum theorists (matter-filled universe, no void) and atomists like Gassendi (indivisible atoms, void space) recognized this division. However, their differing views on matter influenced their accounts of primary qualities. In his chapter on Solidity (II.4), Locke rejects the Cartesian definition of body as mere extension, arguing that bodies are both extended and impenetrable or solid. Solidity, in Locke’s view, distinguishes bodies from void space.

Primary qualities are inherent in objects, independent of perception, such as spatial occupancy, motion or rest, solidity, and texture. Secondary qualities are powers in objects to produce ideas in us, like color, taste, and smell, caused by our sensory apparatus interacting with primary qualities. Ideas of primary qualities resemble the qualities in objects, while ideas of secondary qualities do not resemble their causal powers. Locke also identifies a second class of secondary qualities: powers of substances to affect other substances, e.g., fire’s power to melt wax.

Scholarly debate surrounds the details of Locke’s distinction. Issues include which qualities belong to each category (Locke provides multiple lists), the criteria for categorization (sensory modality?), whether only atoms have primary qualities, and the meaning of “resemblance” between ideas of primary qualities and actual primary qualities. Related is the question of how we know about imperceptible particles. Locke likely believed in analogies between macroscopic objects (porphyry, manna) and their constituent particles, a process Mandelbaum termed “transdiction.” These analogies allow inferences about particle nature and primary/secondary qualities, e.g., atoms are solid, heat is rapid atomic motion, cold is slow motion. However, these analogies may not fully reveal necessary connections between qualities. Another question is whether Locke‘s distinction is reductionistic. If reductionism means primary qualities are real and explain secondary qualities, the answer is unclear. Secondary qualities are indeed primary qualities affecting us, suggesting reductionism. Yet, in Locke‘s II.30 on “real ideas,” both primary and secondary quality ideas are “real.” While secondary quality ideas are caused by primary qualities, primary qualities don’t fully explain them. Locke contends we cannot conceive how particle size, shape, and motion cause sensation in us (IV.3.11–40, N: 544–546).

Locke likely held a representational theory of perception, though some scholars disagree. This theory posits that the mind directly perceives ideas, which are caused by and represent external objects. Perception is thus a triadic relation (object-idea-perceiver) not a dyadic one (object-perceiver) as in naive realism, which suggests direct object perception. Representationalism faces objections, e.g., if ideas are treated as things, they might obscure rather than reveal external objects, like a picture blocking the original. This is sometimes called the “picture/original” theory or, by Jonathan Bennett, the “veil of perception,” suggesting ideas prevent seeing the external world. Nicholas Malebranche arguably held such a view. Antoine Arnauld, while believing in representative ideas, was a direct realist, criticizing Malebranche. Locke follows Arnauld’s critique of Malebranche (Locke, 1823, Vol. IX: 250). However, Berkeley and many later commentators, including Bennett, attribute the veil of perception view to Locke. A.D. Woozley highlights the paradox:

…it is scarcely credible both that Locke should be able to see and state so clearly the fundamental objection to the picture-original theory of sense perception, and that he should have held the same theory himself. (Woozley 1964: 27)

Locke‘s account of perception remains debated. A symposium in the Pacific Philosophical Quarterly (2004, vol. 85, issue 3) found most participants agreeing Locke held a representational theory but wasn’t a skeptic about the external world like the veil of perception view suggests.

Another long-debated issue concerns Locke’s concept of “substance.” The primary/secondary quality distinction helps understand physical objects, but Locke questioned what supports primary qualities and what material and immaterial substances share, leading to his “obscure and relative idea of substance in general.” This is an “I know not what” that supports qualities incapable of existing independently. We perceive clustered properties but infer a supporting substance without directly experiencing it. Locke sees no alternative to substances supporting qualities, rejecting tropes (properties existing independently of substances) and likely rejecting Aristotelian “real qualities,” insisting on substances. He isn’t a skeptic about substance like Hume, but emphasizes the limits of our substance ideas. Bishop Stillingfleet accused Locke of removing substance from the rational world, but Locke didn’t intend this.

Since Berkeley, Locke’s substratum or substance in general doctrine has been criticized as incoherent, implying a property-less particular, seemingly contradicting empiricism (no experience of such entity). Locke acknowledges this problem (I.4.18, N: 95). Michael Ayers proposes interpreting “substratum” and “substance in general” through Locke’s real and nominal essence distinction in Book III, rather than separately. Real essence is atomic constitution, causally grounding observable properties (nominal essence). If real essence were known, observable properties could be deduced. Locke claims real essences of material things are unknown. “Substance in general” is also “something I know not what.” Ayers suggests “substance in general” means “whatever supports qualities,” while real essence means “specific atomic constitution explaining observable qualities.” Thus, Ayers equates unknown substratum with real essence, removing property-less particulars. Critics argue this lacks textual support and contradicts Locke (Jolley 1999: 71–3). As we reach Book III’s essence concept, let’s examine Locke‘s language discussion.

An illustration likely representing Locke’s theory of ideas, showing how sensory input and reflection contribute to our understanding.

2.3 Language and Meaning: Book III of the Essay

Book III of An Essay Concerning Human Understanding is dedicated to language, underscoring Locke’s view of language’s crucial role in knowledge acquisition. He begins by emphasizing abstract general ideas’ importance for knowledge, serving as categories for classifying the vast array of particular existences. Abstract ideas and classification are central to Locke‘s discussion of language and its role in knowledge. Without general terms and classes, knowing the world’s particulars would be impossible.

Book III connects directly to Book II, as Locke asserts words stand for ideas, categorizing words according to Book II’s idea categories: substances, simple modes, mixed modes, relations, etc. Here, Locke introduces the real and nominal essence distinction. His focus on kind terms in classification leads him to prioritize nouns over verbs. Locke acknowledges that not all words relate to ideas, citing particles that “…signify the connexion that the Mind gives to Ideas, or Propositions, one with another” (II.7.1, N: 471). However, the word-idea relationship dominates Book III.

Norman Kretzmann calls “words in their primary or immediate signification signify nothing but the ideas in the mind of him that uses them” (III.2.2) “Locke’s main semantic thesis” (Kretzmann 1968:179). This thesis has been critiqued as a semantic blunder. Mill, for example, argued, “When I say, ‘the sun is the cause of the day’, I do not mean that my idea of the sun causes or excites in me the idea of day” (Mill 1843: bk 1, ch. 2, § 1). This critique mirrors the “veil of perception” critique, suggesting Locke conflates word meaning and reference. Kretzmann argues Locke distinguishes meaning and reference, with ideas providing meaning but not reference. Thus, Mill’s criticism is unfounded.

In addition to idea types, Locke distinguishes particular and abstract ideas. Particular ideas include specific place and time, limiting application to individuals, while abstract general ideas omit these to apply to similar qualities or things. Abstraction and Locke‘s account of it have been much debated. Berkeley argued Locke’s abstraction is incoherent, partly due to Berkeley’s imagism (ideas are images). Imagism makes it difficult to conceive an idea encompassing both right and equilateral triangles. Michael Ayers argues Locke was also an imagist, making Berkeley’s critique relevant. Ayers’ claim is debated (e.g., Soles 1999). Abstraction is vital for human knowledge; Locke believes most words are general (III.1.1, N: 409). Only general or sortal ideas serve in classification.

In discussing substance names and contrasting them with mode names, Locke’s views on language and knowledge emerge. Physical substances are atoms and atom-composed things. We don’t experience horse or table atomic structures, knowing them mainly by secondary qualities (color, taste, smell) and primary qualities (shape, motion, extension). Since real essence (atomic constitution) of “horse” is unknown, the word “horse” cannot derive meaning from it. General words signify a complex of ideas we associate with that kind. These experiential ideas form the nominal essence of a sort.

Classification is central to Book III. How do we categorize things into kinds and organize kinds into species and genera? Aristotelian/Scholastic tradition, rejected by Locke, distinguishes necessary and accidental properties. Necessary properties are essential for an individual’s existence, while accidental properties can change without altering existence. Shared necessary properties define natural kind essences. Kind boundaries are sharp and determinate. Aristotelian science aims to discover natural kind essences, organizing kinds hierarchically into a privileged classification reflecting world structure. This is Aristotelian essentialism. Locke rejects aspects of this, denying individual essences apart from kind membership and a single privileged natural classification. He argues for multiple classifications, each useful for different purposes.

Locke’s pragmatic language view and nominal/real essence distinction offer an anti-essentialist alternative to Aristotelian essentialism and natural kind classification. He claims no fixed natural boundaries exist between species; boundaries are fuzzy with borderline cases. Debate exists whether Locke saw this fuzziness at both nominal/appearance and real/atomic levels, or just nominal. The first view is no Aristotelian natural kinds at either level. The second is Aristotelian natural kinds exist at the atomic level, but are unknowable. Either way, real essence cannot define substance names’ meaning. Lovejoy (Great Chain of Being) and Wiggins support the second view, while Ayers and Uzgalis argue for the first (Uzgalis 1988; Ayers 1991: II. 70).

Conversely, nominal essences are derived from experience. Locke argues the mind actively constructs sorts, with numerous properties to choose from, leading to varied ideas of substance essences. Some interpret this as arbitrary conventionalism with no basis for criticizing nominal essences. Locke sometimes suggests this, but this impression should be resisted. Peter Anstey characterizes Locke’s conventionalism as constrained and convergent (Anstey 2011: 209, 212). Locke states nominal essence construction is mental work, constrained by usage (words representing existing ideas) and substance words aiming to represent substance properties. He says kind ideas are archetypes of property complexes causing appearances used for nominal essences and unifying regularly conjoined ideas. Archetypes imply constraints on property combinations (and thus ideas). Without constraints, no archetype exists. (For further discussion, see entry Locke on Real Essences).

Consider word usage. Consistent meaning within a language community is crucial for communication, language’s primary function. Misusing words hinders effective communication, defeating language’s purpose. However, Locke acknowledges usage traditions can evolve, enabling improved knowledge and understanding through clearer, more precise ideas.

Substance name creation involves discovery (e.g., violets, gold), naming the idea, and linguistic introduction. Language is seen as a tool for everyday prosaic purposes. Ordinary people are primary language creators.

Vulgar Notions suit vulgar Discourses; and both though confused enough, yet serve pretty well for the Market and the Wake. Merchants and Lovers, Cooks and Taylors, have Words wherewith to dispatch their ordinary affairs; and so, I think, might Philosophers and Disputants too, if they had a mind to understand and to be clearly understood. (III.11.10, N: 514)

Ordinary people use apparent qualities, mainly secondary qualities, to form ideas and words for their needs.

Natural philosophers (scientists) later investigate whether property connections within ordinary ideas hold true in nature, seeking necessary property connections. Yet, even scientists, in Locke’s view, are limited to observable (mainly secondary) qualities for categorization. Scientists may correct popular errors, like classifying whales as fish. Whales are mammals, possessing mammal qualities, not fish qualities. Classifying whales as fish is a mistake. Similarly, a gold idea solely based on softness and color would fail to distinguish gold from fool’s gold. While the mind constructs complex ideas (“workmanship of the understanding”), and can combine ideas arbitrarily, the resulting product is open to criticism for deviating from usage or inadequately representing archetypes. This criticism aims to enhance human understanding of the material world and improve the human condition. This is the convergent aspect of Locke‘s conventionalism. Nominal essence accuracy converges on real essence.

However, remember Locke’s “master-builders.” Stephen Gaukroger (2010) argues Locke philosophically justified experimental philosophy like Boyle’s air pump work, Boyle and Newton’s color research, and Sydenham’s observational medicine, all criticized for lacking matter theory explanations. Locke justifies experimental philosophy’s autonomy. Experimental explanations rely solely on phenomenal relations, even with micro-corpuscular bases. Gaukroger sees this as Locke’s contribution to mechanism’s collapse. See Gaukroger (2010), Chapters 4 and 5, for details.

The mode-substance distinction is crucial in Locke’s philosophy. Modes, unlike substances, are dependent existences—orderings of substances. These are technical terms for Locke. He defines:

First, Modes I call such complex Ideas, which however compounded, contain not in themselves the supposition of subsisting by themselves; such are the ideas signified by the Words Triangle, Gratitude, Murther, etc. (II.12.4, N: 165)

Locke distinguishes simple and mixed modes:

Of these Modes, there are two sorts, which deserve distinct consideration. First, there are some that are only variations, or different combinations of the same simple Idea, without the mixture of any other, as a dozen or score; which are nothing but the ideas of so many distinct unities being added together, and these I call simple Modes, as being contained within the bounds of one simple Idea. Secondly, There are others, compounded of Ideas of several kinds, put together to make one complex one; v.g. Beauty, consisting of a certain combination of Colour and Figure, causing Delight to the Beholder; Theft, which being the concealed change of the Possession of any thing, without the consent of the Proprietor, contains, as is visible, a combination of several Ideas of several kinds; and these I call Mixed Modes. (II.12.5, N: 165)

Mode ideas are also mind-constructed, but archetypes are mental. The question is whether worldly things fit our ideas, not vice versa. Our ideas are adequate. Defining “bachelor” as unmarried, adult, male human, non-fitting individuals simply aren’t bachelors. Modes provide ideas for mathematics, morality, religion, politics, and conventions. Modal ideas are mind-made standards, making them clear, distinct, adequate, and complete, combining real and nominal essences. Mathematical terms have precise definitions (necessary and sufficient conditions), and mathematical truths are deductively demonstrable. Locke suggests morality is also deductively demonstrable, though he never produced such a system despite Molyneux’s urging. Entry Locke’s moral philosophy explores Locke‘s morality in detail. Political discourse terms also have modal aspects. Locke’s definitions of state of nature, slavery, war in Second Treatise are likely modal definitions with deductive consequences. However, politics may require both experience and deductive modal analysis.

2.4 Knowledge, Probability, and the Limits of Certainty: Book IV

In Book IV of An Essay Concerning Human Understanding, Locke defines knowledge, exploring human knowledge capacities and limitations. He defines knowledge as “the perception of the connexion and agreement or disagreement and repugnancy of any of our Ideas” (IV.1.1, N: 525). This definition contrasts with Descartes’ clarity and distinctness criterion. Locke’s definition allows for knowledge of substances, despite their inclusion of the obscure “substance in general” idea. However, this raises a problem analogous to perception and language: is knowledge confined to our own ideas? How do we know real existence? Locke likely believed the implausibility of skeptical hypotheses (like Descartes’ Dream Hypothesis, not even mentioning the Evil Demon) and causal connections between qualities and ideas within his system sufficiently address this. Differences between Locke‘s empiricism and Berkeley’s ease Locke‘s solution to the veil of perception problem compared to Berkeley. Locke makes transdictive inferences about atoms, which Berkeley rejects, implying Locke has a semantics allowing talk of unexperienced causes (atoms), unlike Berkeley. (See Mackie’s discussion in Problems from Locke, 1976: 51–67.)

What can we know and with what certainty? We can know God’s existence with near-certainty (demonstration). We know our own existence with highest certainty. Morality and mathematics are also knowable with certainty as modal ideas, whose adequacy is ensured by being ideal models, not copies of external archetypes. Our grasp of external object nature is limited to apparent quality connections. Elephant and gold real essences are hidden, though we assume atomic combinations cause apparent quality groupings distinguishing elephants, violets, gold, lead. Our material world knowledge is probabilistic opinion, inferior to mathematical, moral, self, and God knowledge. We have sensitive knowledge of external objects, limited to present experience. While Locke limits knowledge scope, he believes we can judge truth/falsity of many propositions beyond knowledge, leading to probability.

2.5 Navigating Uncertainty: Knowledge and Probability in Locke’s Thought

Knowledge, for Locke, is perceiving agreement or disagreement between ideas. What is probability, and how does it relate? Locke explains:

The Understanding Faculties being given to Man, not barely for Speculation, but also for the Conduct of his Life, Man would be at a great loss, if he had nothing to direct him, but what has the Certainty of true Knowledge… Therefore, as God has set some Things in broad day-light; as he has given us some certain Knowledge…So in the greater part of our Concernment, he has afforded us only the twilight, as I may say so, of Probability, suitable, I presume, to that State of Mediocrity and Probationership, he has been pleased to place us in here, wherein to check our over-confidence and presumption, we might by every day’s Experience be made sensible of our short sightedness and liableness to Error… (IV.14.1–2, N: 652)

Beyond limited certain knowledge (self, God, math, morality), life mostly requires navigating without certainty. What is probability? Locke writes:

As Demonstration is the shewing of the agreement or disagreement of two Ideas, by the intervention of one or more Proofs, which have a constant, immutable, and visible connexion one with another: so Probability is nothing but the appearance of such an Agreement or Disagreement, by the intervention of Proofs, whose connection is not constant and immutable, or at least is not perceived to be so, but is or appears, for the most part to be so, and is enough to induce the Mind to judge the Proposition to be true, or false, rather than the contrary. (IV.15.1, N: 654)

Probable reasoning is argument-like, similar to demonstrative reasoning for knowledge, but with crucial differences. It provides evidence inclining the mind to judge truth or falsity, without certainty. Probable judgments have degrees, from near-demonstrations to near-impossibilities, correlated with assent degrees from full assurance to doubt.

Mathematical probability was emerging when Locke wrote the Essay, but his probability account shows little awareness of it, reflecting older traditions treating testimony as probable reasoning. Given Locke‘s aim to discuss assent to religious propositions, this older probability concept likely suited his purpose. Locke grounds probability in proposition conformity to knowledge, observation, experience, and testimony. Testimony involves witness number, integrity, observational skill, counter-testimony, etc. Rational assent to probable propositions requires considering these. Locke also suggests tolerance for differing opinions, favoring retaining existing opinions over adopting those of strangers or adversaries with vested interests.

Locke distinguishes two probable proposition types: particular existences/matters of fact and matters beyond sensory testimony. Matters of fact are observable and experiential, allowing application of rational assent tests. Matters beyond senses (finite immaterial spirits like angels, atoms, extraterrestrial life) require analogy for reasoning.

Thus the observing that the bare rubbing of two bodies violently one upon the other, produce heat, and very often fire it self, we have reason to think, that what we call Heat and Fire consist of the violent agitation of the imperceptible minute parts of the burning matter…. (IV.16.12, N: 665–6)

Reasoning about angels involves the Great Chain of Being, inferring species above us are as numerous as those below. However, this reasoning is only probable.

2.6 Reason, Faith, and the Perils of Enthusiasm

The respective roles of senses, reason, and faith in attaining truth and guiding life were major issues. James Tyrrell noted Essay‘s impetus was a discussion of morality and revealed religion. Book IV Chapters 17, 18, and 19 address reason, reason-faith relation, and enthusiasm. Locke notes all sects use reason as far as possible, resorting to faith (revelation above reason) only when reason fails. He adds:

And I do not see how they can argue with anyone or even convince a gainsayer who uses the same plea, without setting down strict boundaries between faith and reason. (IV.18.2, N: 689)

Locke defines reason as

the discovery of the certainty or probability of such propositions or truths, which the mind arrives at by deduction made from such ideas, as it has got by the use of its natural faculties; viz, by the use of sensation or reflection. (IV.18.2, N: 689)

Faith is assent to propositions “…upon the credit of the proposer, as coming from God, in some extraordinary way of communication”. Faith is belief in revelation, undiscoverable by reason. Locke distinguishes original revelation (God to a person) and traditional revelation (original revelation “…delivered over to others in Words, and the ordinary ways of our conveying our Conceptions one to another” (IV.18.3, N: 690)).

Locke notes some things are discoverable by both reason and revelation (Euclid’s geometry revealed). In such cases, faith is less useful. Traditional revelation never offers certainty comparable to contemplating idea agreement/disagreement. Factual revelations are less certain than direct experience. Revelation cannot contradict known truths, as this undermines faculty trustworthiness, a disastrous outcome. Revelation’s domain is where reason is absent.

…that Part of the Angels rebelled against GOD, and thereby lost their first happy state: and that the dead shall rise, and live again: These and the like, being Beyond the Discovery of Reason, are purely matters of Faith; with which Reason has nothing to do. (IV.18.8, N: 694)

Yet, reason plays a crucial role concerning revelation. Locke writes:

Because the Mind, not being certain of the Truth of that it evidently does not know, but only yielding to the Probability that appears to it, is bound to give up its assent to such Testimony, which, it is satisfied, comes from one who cannot err, and will not deceive. But yet, it still belongs to Reason, to judge of the truth of its being a Revelation, and of the significance of the Words, wherein it is delivered. (IV.18.8, N: 694)

Reason and probability judge revelation genuineness. Without clear faith-reason boundaries, religion lacks reason, leading to “extravagant Opinions and Ceremonies…in the religions of the world…” (IV.18.11, N: 696).

Accepting revelation without reason leads to enthusiasm, a third assent principle beyond reason and revelation. Enthusiasm is unfounded confidence in divine favor or communication, negating reason’s role in judging genuineness. Spurious communications are “ungrounded Fancies of a Man’s own Brain” (IV.19.2, N: 698). Enthusiasm, common among Protestant extremists since the Civil War, is strongly rejected by Locke. Enthusiasm violates the principle of proportional assent to evidence, catastrophic to abandon. Locke reiterates this in Conduct of the Understanding and Reasonableness of Christianity. He urges individual reason in truth-seeking. Of enthusiasts, Locke writes:

…he that takes away Reason to make way for Revelation, puts out the Light of both, and does much what the same, as if he would perswade a Man to put out his eyes, the better to receive the remote Light of an invisible Star by a Telescope. (IV.19.4, N: 698)

Enthusiasts bypass reasoning about revelation genuineness, self-persuaded of immediate revelation, leading to “odd Opinions and extravagant actions,” warning against this principle. Locke rejects inward persuasion unjudged by reason as a legitimate principle.

3. Locke’s Educational Philosophy: Shaping Minds for Liberty

Locke’s educational works, Some Thoughts Concerning Education and Conduct of the Understanding, bridge Essay Concerning Human Understanding and his political writings. Grant and Tarcov note:

The idea of liberty, so crucial to all of Locke’s writings on politics and education, is traced in the Essay to reflection on the power of the mind over one’s own actions, especially the power to suspend actions in the pursuit of the satisfaction of one’s own desires until after a full consideration of their objects (II.21.47, N: 51–52). The Essay thus shows how the independence of mind pursued in the Conduct is possible. (G&T 1996: xvi)

Some Thoughts Concerning Education, published in 1693, compiled advice Locke gave Edward Clarke about his son’s (and daughters’) education since 1684. While revising Essay‘s fourth edition, Locke began “Conduct of the Understanding,” which became lengthy and unfinished. Posthumously published by Peter King in 1706, Conduct and Thoughts complement each other. Thoughts focuses on parental child education, Conduct on adult self-education (G&T 1996: vii), though Grant and Tarcov note tensions illustrating liberal society paradoxes. Thoughts targets English gentry sons and daughters in the late 17th century, more time and place-specific than Conduct. However, its emphasis on virtues like

justice as respect for the rights of others, civility, liberality, humanity, self-denial, industry, thrift, courage, truthfulness, and a willingness to question prejudice, authority and the biases of one’s own self-interest

represents qualities for liberal society citizens (G&T 1996: xiii).

Locke’s Thoughts culminates a century of “child discovery.” In the Middle Ages, children were seen as mere playthings, miniature adults, with age and differentiated education unimportant (Axtell 1968: 63–4). Locke treated children as developing rational beings needing parental fostering of rationality. He urged parental time with children, tailoring education to individual character, developing body and character, and using play over rote learning and punishment. He advocated language learning through conversation before grammar rules and suggested children learn a manual trade.

Advocating education fostering independent thinking, Locke prepared people for self-governance and civic participation. Conduct reveals connections between reason, freedom, and morality. Reason, free from partiality and passion, questioning authority, leads to fair judgment and action, essential for self-government. We have a duty to cultivate reason to avoid moral failings (G&T 1996: xii), Locke’s “education for liberty” (Tarcov).

4. The Two Treatises of Government: Foundations of Liberal Political Thought

Lord Shaftesbury, dismissed as Lord Chancellor in 1673, became a Country Party leader. In 1679, the central issue was excluding James, Duke of York, from succeeding Charles II due to James’ Catholicism in Protestant England. The Country Party, with a Commons majority, passed an Exclusion Bill, but the King’s opposition led to its failure in the Lords. Repeated attempts failed. Parliamentary failure led some Country Party leaders to plot armed rebellion.

Two Treatises of Government was published in 1689, after the failed rebellion and Shaftesbury’s death in exile. The introduction suggested justification for the Glorious Revolution of 1688. However, Two Treatises was written during the Exclusion Crisis in 1681, possibly intended to justify a planned Country Party uprising.

Rebellion to exclude James faced obstacles. Anglican gentry support was needed, but Anglican doctrine emphasized obedience to terrestrial superiors, allowing passive resistance under conscience but not active resistance (Dunn, 1968, 48). By 1679, King’s opposition to exclusion was clear; exclusion meant “explicit and self-conscious resistance to the sovereign.” Passive resistance was insufficient. Yet, royal policy “outraged their deepest religious prejudices and stimulated their most obscure emotional anxieties.” Gentry were conflicted. Dunn notes: “To exert influence upon their choice it was above all necessary to present a more coherent ordering of their values, to show that the political tradition within which the dissenters saw their conduct was not necessarily empirically absurd or socially subversive. The gentry had to be persuaded that there could be reason for rebellion which could make it neither blasphemous or suicidal.” (Dunn, 1968, 49). To achieve this, Locke attacked the most relevant divine right of kings advocate, Sir Robert Filmer (c 1588–1653), whose posthumous Patriarcha (1680) was the most complete exposition of the view Locke opposed. Filmer argued for men’s birth into servitude, social hierarchy, and a sovereign constrained only by God, making passive obedience the only option, and resistance “vicious, blasphemous and intellectually absurd.” Locke needed to refute Filmer and “rescue the contractarian account of political obligation from the criticism of impiety and absurdity,” restoring “to the Anglican gentry a coherent basis for moral autonomy or a practical initiative in the field of politics.” (Dunn, 1968, 50).

The First Treatise of Government refutes the theological basis for patriarchal divine right of kings doctrine by Filmer. Locke targets Filmer’s claim that men are not “naturally free,” the “ground” for Filmer’s argument that “legitimate” government is “absolute monarchy,” with kings descended from Adam and subjects naturally slaves. Early in First Treatise, Locke denies scriptural or rational support for Filmer’s claims, minutely examining biblical passages.

The Second Treatise of Government presents Locke‘s positive government theory and continues refuting Filmer’s absolute monarchical power. Locke argues Filmer’s view leads to governments based on force, necessitating an alternative account of government origin “lest men fall into the dangerous belief that all government in the world is merely the product of force and violence” (Treatises II,1,4). Locke employs natural rights theory and the social contract, common in 17th and 18th-century political philosophy. Natural rights are pre-governmental human rights, like the right to survival. Locke argues for a right to survival means. Social contract theory explains government origin through people agreeing to transfer rights to government while retaining others. 17th and 18th-century natural rights and social contract theories varied from conservative to radical. Locke‘s is radical, influencing American and French Revolutions.

Locke’s strategy to refute Filmer is showing Filmer conflates limited powers (over wives, children, servants, slaves, subjects), falsely implying absolute royal power. Distinguishing these and their limits clarifies monarchs lack legitimate absolute power over subjects.

4.1 The Second Treatise: Outlining Legitimate Government

A key aim in Second Treatise is defining legitimate government to distinguish it from illegitimate forms, establishing a basis for legitimate revolution. Examining existing complex governments to define legitimate government is difficult. Locke‘s strategy, like Hobbes and others, is considering life without civil government, a simpler state (state of nature) to understand government’s proper role. Chapter 1 defines political power:

Political power, then, I take to be a right of making laws with penalties of death, and consequently all less penalties, for the regulating and preserving of property, and of employing the force of the community, in the execution of such laws, and in the defence of the common-wealth from foreign injury; and all this only for the public good. (Treatises, II, 1,3)

Chapter 2 describes the state of nature, lacking government with political power. State of nature is sometimes mistakenly seen as government-less. It can be government-less, illegitimate government, or legitimate government with limited power. (See state of nature in Locke’s political philosophy entry.)

Pre-government state of nature is politically equal, lacking natural superiors/inferiors. Equality yields mutual love obligation, duties, and justice/charity maxims. Was there ever such a state? Debate exists. Hobbes and Locke likely answer affirmatively. Lacking common political authority implies state of nature. Like being naturally single until married. Locke finds state of nature in his time in “inland, vacant places of America” (Second Treatise V. 36) and inter-people relations. State development might also involve state of nature stages. Alternatively, state of nature may be a theoretical construct, defining government’s function. Even rejecting historicity, it’s analytically useful. For Locke, it’s likely both historical and theoretical.

4.2 Human Nature, Natural Rights, and Divine Purpose in Locke

For Locke, God created humanity; we are God’s property. Our chief end as species and individuals is survival, divinely ordained. A wise, omnipotent God created humans for His purposes:

…by his order and about his business, they are his property whose workmanship they are, made to last during his, not one another’s pleasure: and being furnished with like faculties, sharing all in one community of nature, there cannot be supposed any subordination among us, that may authorize us to destroy one another, as if we were made for one another’s uses, as the inferior ranks of creatures are for our’s. (Treatises II,2,6)

Thus, “he has no liberty to destroy himself, or so much as any creature in his possession, yet when some nobler use than its bare possession calls for it” (Treatises II.2.6). Murder and suicide violate divine purpose.

If survival is the end, means are life, liberty, health, and property. Divinely ordained end implies rights to means. Thus, we have rights to life, liberty, health, and property. These are natural rights, pre-governmental, equally possessed by all.

Natural law also exists, the Golden Rule in natural rights terms:

The state of nature has a law of nature to govern it, which obliges everyone: and reason which is that law, teaches all mankind who will but consult it, that being all equal and independent, no one ought to harm another in his life, health, liberty or possessions…. (Treatises II.2.6)

Natural law is revealed by reason, commanding what’s best for us. Otherwise, it wouldn’t be obeyed. Reason reveals natural law through reflecting on self and others’ best interests, given survival and equality. (See natural law in Locke’s political philosophy entry.)

Locke doesn’t portray state of nature as utopia, but as an analytical tool explaining civil government’s necessity and function. State of nature has problems. Natural law, like civil law, can be violated. No police, prosecutors, judges exist in state of nature. Victims enforce natural law. We have rights to enforce law and judge on our own behalf, and may assist others. This right justifies legitimate rebellion. However, wronged parties are likely to judge crimes more severely, leading to miscarriages of justice, a major state of nature problem.

4.3 War, Slavery, and the Boundaries of Power

In chapters 3 and 4, Locke defines states of war and slavery. State of war is a sedate, settled intention to violate life right (and all other rights), placing the aggressor in war with the intended victim. The aggressor is unjust. This deviates from Hobbes equating state of nature and war. For Locke, state of nature is typically Golden Rule-governed, fostering love. War arises from rights violations. Locke’s war theory always has an innocent victim and unjust aggressor.

Slavery is absolute or arbitrary power of another. Legitimate slavery arises only from being an unjust aggressor defeated in war. The victor may kill or enslave. Slavery is continued war between victor and captive, where victor delays killing, using the captive instead. Slavery ends with compacts for obedience and limited power, becoming master-servant relations, as “no man, can, by agreement pass over to another that which he hath not in himself, a power over his own life” (Treatises II.4.24). Legitimate slavery defines despotic power’s limits and illuminates illegitimate slavery: absolute power without just cause, which Locke argues absolute monarchs impose on subjects. Slavery chapter is crucial in Locke‘s Filmer refutation.

However, debate persists about Locke‘s slavery theory justifying Afro-American slavery, given his trade and colonial government involvement. If so, his philosophy wouldn’t contradict his actions. However, this view faces strong objections. Justifying Afro-American slavery would require a broader legitimate slavery definition than Locke‘s narrow one. Some suggest Locke‘s “just war” is vague enough to twist for Afro-American slavery, but this is also questionable. Chapter “Of Conquest” explicitly limits conqueror power. Limits on legitimate slaves and just conqueror powers condemn 17th-19th century Afro-American slavery. Debate continues, partly fueled by Locke‘s role in Fundamental Constitutions of the Carolinas, which included a provision for absolute power over negro slaves. Wilson’s The Ashley Cooper Plan (2016) details Ashley Cooper’s Carolina intentions and how Barbadian slave owners altered Carolina into a slave society. Roper (Conceiving Carolina, 2004) offers a different account focusing on Indian slave trade conflicts. Farr (“Locke, Natural Law and New World Slavery,” 2008) argues Locke intended slavery theory for English absolutism, not Afro-American slavery, but notes slavery involvement ruins his liberty champion reputation. Woolhouse (Locke: A Biography, 2007: 187) remarks “glaring contradiction between his theories and Afro-American slavery.”

Recent debate questions whose slavery and absolutism theory Locke attacked. Olsthoorn and van Apeldoorn (2020) argue Locke’s account of self-enslavement and absolute rule lacks force against Grotius and Puffendorf, who defended absolutism and colonial slavery.

Waldmann (“Slavery and Absolutism in Locke’s Two Treatises: A Response to Olsthoorn and van Apeldoorn”) refutes some of their claims, finding others irrelevant. He disputes: 1) Locke‘s idiosyncratic slavery/absolute rule conception is rejected by absolutist thinkers; 2) Like Filmer, Locke believes absolute rulers arbitrarily kill subjects due to dominium; 3) Early modern natural lawyers conceptualized slavery differently, not as ownership of destroyable things (Waldmann 7).

Waldmann argues Filmer accurately represented Royalist positions in the 1670s/80s, making Locke‘s account not a straw man. Olsthoorn and van Apeldoorn wrongly attribute Filmer’s view to Locke. Waldmann agrees Locke‘s slavery position differs significantly from Grotius and Puffendorf, weakening its force against them, but this is unimportant as Locke wasn’t arguing against them. A plausible suggestion is Locke targeted Hobbes’ self-enslavement and royal dominium assertions.

Uzgalis (“John Locke, Slavery and Indian Lands,” 2017) argues for Locke having two slavery theories: legitimate and illegitimate. Olsthoorn and van Apeldoorn miss this distinction. While Locke shares dominium slavery with Filmer (master can kill/maim), neither theory belongs to Filmer. If Locke is right about royal absolutism and slave trade/colonial slavery practices, both fall under illegitimate slavery. Grotius, Puffendorf, and Hobbes lack explicit illegitimate slavery theories. Uzgalis notes Grotius and Puffendorf offered arguments Locke could have used to justify slave trade/colonial slavery, but Locke rejects them, weakening his absolutism argument, suggesting he crafted an alternative theory, possibly against Hobbes.

Brewer (“Slavery, Sovereignty, and ‘Inheritable Blood’,” 2017) argues Stuart kings, Charles II and James, Duke of York, promoted Royal Africa Company, slave trade, and colonial slavery for royal revenue. James, Duke of York, was Royal Africa Company Governor, and Shaftesbury, Locke’s patron, was sub-governor with Locke’s assistance. James attacked Dutch African forts for Royal Africa Company bases. Stuarts minted guinea coins celebrating these efforts. James continued as Royal Africa Company Governor as King. Brewer highlights absolutism-slave trade/colonial slavery links, seeing slavery spread as English imperial policy. She argues Locke, on William III’s Board of Trade, sought to undo Stuart slavery policies.

4.4 Property Rights and the Rise of Economic Inequality

Chapter 5, “Of Property,” is influential and controversial in Second Treatise. It describes state of nature evolution leading to civil government, not just private property origin (see property in Locke’s political philosophy entry).

Locke begins property discussion noting God gave earth to all in common, raising the question of private property origin, a serious difficulty. However, we are meant to use earth “for the best advantage of life and convenience” (Treatises II.5.25). Private property doesn’t arise from universal consent. Asking everyone for berry permission would lead to starvation. We have property in our person, and our labor belongs to us. Picking acorns or berries makes them the picker’s property. Daniel Russell argues Locke‘s labor is goal-directed activity converting potential resources into actual resources (Russell 2004), connecting to natural law obligation of self-preservation and helping others.

Acquisition isn’t unlimited. Locke introduces waste limitation:

As much as anyone can make use of to any advantage of life before it spoils, so much by his labor he may fix a property in; whatever is beyond this, is more than his share, and belongs to others. (Treatises II.5.31)

Initially, small populations and abundant resources meant little property contention, as individuals could use only a small portion.

Locke initially discusses hunter-gatherer property and its rational limitations. He then shifts to agriculture and land ownership and its limitations. State of nature evolves from hunter-gatherer to agricultural society. Labor limits land enclosure to what one can work. Another limitation is:

Nor was this appropriation of any parcel of land, by improving it, any prejudice to any other man, since there was still enough, and as good left; and more than the as yet unprovided could use. So that, in effect, there was never the less for others because of his inclosure for himself: for he that leaves as much as another can make use of, does as good as take nothing at all. No body could consider himself injured by the drinking of another man, though he took a good draught, who had a whole river of the same water left to quench his thirst: and the case of land and water, where there is enough, is perfectly the same. (Treatises II.5.33)

Next state of nature evolution involves money. Locke notes:

… before the desire of having more than one needed had altered the intrinsic value of things, which depends only on their usefulness to the life of man; or had agreed, that a little piece of yellow metal, which would keep without wasting or decay, should be worth a great piece of flesh, or a whole heap of corn; though men had a right to appropriate by their labor, each one of himself, as much of the things of nature, as he could use; yet this could not be much, nor to the prejudice of others, where the same plenty was left to those who would use the same industry. (Treatises II.5.37)

Pre-money, economic equality was imposed by reason and barter. Needs and conveniences were largely limited. Necessities are perishable (berries, venison). Bartering berries for longer-lasting nuts was reasonable.

…if he would give his nuts for a piece of metal, pleased with its color, or exchange his sheep for shells, or wool for a sparkling pebble or diamond, and keep those by him all his life, he invaded not the right of others, he might heap up as much of these durable things as he pleased; the exceeding of the bounds of his property not lying in the largeness of his possessions, but the perishing of anything uselessly in it. (Treatises II.5.146)

Money allows differential property increase and economic inequality. Without money, exceeding earlier economic equality is pointless. Money economy allows vastly different proportions based on industry.

This partage of things in an inequality of private possessions, men have made practicable out of the bounds of society, and without compact, only by putting a value on gold and silver, and tacitly agreeing to the use of money: for in governments, the laws regulate the rights of property, and the possession of land is determined by positive constitutions. (Treatises II.5.50)

Money introduction causes inequality, multiplying quarrels, contentions, and natural law violations, leading to civil government. What happens to property acquisition qualifications after money? Macpherson (Possessive Individualism) argues qualifications are discarded, allowing unlimited private property acquisition. This may not be fully correct. Non-spoilage is satisfied as money doesn’t spoil. Other qualifications become less relevant due to civil society property conventions. Did Locke approve of these changes? Macpherson sees Locke as proto-capitalist, advocating unlimited wealth. Tully (Discourse of Property) sees Locke as criticizing self-interest and economic inequality arising from money as a fall of man. This interpretative difference has been debated for decades. Second Treatise may be ambiguous. Consider Locke’s Some Thoughts Concerning Education:

Covetousness and the desire to having in our possession and our dominion more than we have need of, being the root of all evil, should be early and carefully weeded out and the contrary quality of being ready to impart to others inculcated. (G&T 1996: 81)

Let’s turn to civil government institution.

4.5 The Social Contract and the Consent of the Governed

Social contract theory flourished in the 17th and 18th centuries. Why is Locke a social contract theorist? Was it merely a prevailing idea he adopted? No. Locke‘s project strongly pushes him toward social contract. Governments could be seen as force-instituted without agreement. Adopting this view would contradict Locke‘s Second Treatise project, though Norman conquest-like cases force him to admit citizen acceptance of initially forced government. Remember Second Treatise presents Locke‘s positive government theory, explicitly opposing the view

that all government in the world is merely the product of force and violence, and that men live together by no other rules than that of the beasts, where the strongest carries it … . (Treatises II, 1, 4)

While admitting some governments arise by force, Locke would undermine the legitimate/illegitimate government distinction if legitimate government could originate this way. Legitimate government, for Locke, is instituted by explicit consent of the governed. (See consent, political obligation in Locke’s political philosophy entry.) Consenting individuals transfer natural law enforcement and self-judgment rights to government, legitimizing governmental justice systems.

Ruth Grant argues government establishment is a two-step process. Universal consent forms political community. Community membership consent is binding and irrevocable, ensuring community stability. Grant writes: “Having established that the membership in a community entails the obligation to abide by the will of the community, the question remains: Who rules?” (1987: 114–115). Majority rule answers this question. Universal consent establishes political community; majority consent decides rulers. These consents differ in kind, not just degree. Grant:

Locke’s argument for the right of the majority is the theoretical ground for the distinction between duty to society and duty to government, the distinction that permits an argument for resistance without anarchy. When the designated government dissolves, men remain obligated to society acting through majority rule. (1987: 119)

Majority can confer rule on a king, oligarchs, or democratic assembly. Social contract isn’t inherently democratic. However, any government must fulfill civil government’s legitimate function.

4.6 The Purpose and Limits of Civil Government

Locke can now define legitimate government function and distinguish it from illegitimate forms. Legitimate government aims to preserve citizen rights to life, liberty, health, and property, prosecuting rights violators and pursuing public good, even conflicting with individual rights. It provides impartial judgment unavailable in state of nature, setting proportionate punishment, a key improvement over state of nature. Illegitimate government fails to protect citizen rights, claiming despotic power to violate them. Locke, arguing against Filmer equating patriarchal and political power as despotic power, distinguishes these three powers in chapter 15 “Of Paternal, Political and Despotic Power Considered Together”:

THOUGH I have had occasion to speak of these before, yet the great mistakes of late about government, having as I suppose arisen from confounding these distinct powers one with another, it may not be amiss, to consider them together.

Chapters 6 and 7 detail paternal and political power respectively. Paternal power is limited to childhood minority. Political power, derived from transferred individual natural law enforcement power, includes right to kill for citizen rights or public good. Despotic power, in contrast, claims right to take life, liberty, health, and property arbitrarily.

4.7 Legitimate Rebellion and the Right to Resist Tyranny

The Second Treatise concludes by examining illegitimate civil governments and conditions for legitimate rebellion and regicide. Scholars believe the book was written during the Exclusion Crisis, possibly justifying insurrection and regicide against the King and his brother. Legitimate revolution argument follows from distinguishing legitimate and illegitimate government. Legitimate government protects citizen rights (life, health, liberty, property) within public good, deserving obedience. Illegitimate government systematically violates citizen natural rights, seeking to illegitimately enslave them, placing itself in state of nature and war with subjects. Illegitimate magistrate or king violates natural law, becoming a dangerous predator operating on “might makes right.” Rebellion and killing such predators are legitimate. Locke justifies rebellion and regicide in certain cases, potentially justifying regicide against the English King and his brother had the Rye House Plot succeeded. Even if unintended, it served this purpose.

5. Religious Toleration: Locke’s Vision for a Pluralistic Society

Religious toleration was a central concern in 17th-century Europe due to widespread religious intolerance and violence. The Reformation divided Europe into religious factions, causing civil wars and persecutions. John Marshall notes the 1680s as a peak decade for persecution. The Dutch Republic, where Locke was exiled, was founded as a secular state allowing religious diversity, reacting to Catholic persecution of Protestants. However, Calvinist dominance led to persecution of dissenting sects like Remonstrants. Yet, the Dutch Republic remained Europe’s most tolerant nation. France’s religious conflict was temporarily eased by the Edict of Nantes, but Louis XIV revoked it in 1685, persecuting Huguenots. Some 200,000 Huguenots emigrated, and 700,000 were forced to convert to Catholicism. England was acutely aware of French events.

Religious conflict dominated 17th-century England, contributing to the Civil War and Anglican Church abolition during the Protectorate. After the Restoration, Anglican Parliament repressed Catholics and Protestant sects (Presbyterians, Baptists, Quakers, Unitarians) disagreeing with the state church. King Charles and Shaftesbury both valued religious toleration, but diverged on targets: King focused on Catholics, Shaftesbury on Protestant dissenters.

Comprehension, a strategy to reduce religious conflict, aimed to minimize Anglican doctrine and practices to include most dissenting sects in the state church, with toleration for remaining sects (state non-persecution). Neither strategy progressed much during the Restoration.

After fleeing to Holland, Locke joined a religious toleration advocacy group including Benjamin Furly, Pierre Bayle, Dutch theologians, and others. This group debated intolerance arguments in book clubs, considering toleration for Protestants, dissenters, Jews, Muslims, and Catholics. Recent discovery shows Locke considered Catholic toleration pros and cons (Walmsley and Waldmann 2019). Some group members wrote tolerationist works and journals promoting free speech, civility, and politeness, calling themselves “Republic of Letters” or “Locke’s commonwealth of learning.”

Locke’s religious views are complex. Religion, particularly Christianity, deeply influenced his philosophy. Was he an orthodox Anglican, Latitudinarian, or dissenter? Locke claimed Anglicanism until death, and his biographer Fox Bourne agreed. Latitudinarians sought reasonable Christianity acceptable to dissenters. However, evidence suggests Locke was neither orthodox Anglican nor Latitudinarian. He prompted Newton to write an anti-Trinitarian tract (McLachlan 1941), suggesting Locke was Arian or Unitarian, rejecting Trinity doctrine. His Letter on Toleration advocating church-state separation doesn’t align with state religion devotion. Reasonableness of Christianity, arguing for minimal, reason-compatible Christian doctrines, might seem Latitudinarian. However, Ashcraft argues Anglican comprehension meant dissent abandonment. Latitudinarians were “acceptable face of persecution of religious dissent” (Ashcraft 1992: 155), not moderate middle ground. Ashcraft distinguishes Anglican and dissenting “rational theologies.” While Locke had Latitudinarian friends, Reasonableness of Christianity might be dissenting “rational theology.”

Locke considered religious toleration since 1659, with evolving views. Early 1660s, likely orthodox Anglican. He and Shaftesbury enacted toleration in Fundamental Constitutions of the Carolinas (1669). He wrote Epistola de Tolerantia (1685) in Dutch exile, witnessing Huguenot refugees. Holland, despite Calvinist theocracy issues, was more tolerant. Locke’s Letter gives principled religious toleration account, mixed with arguments specific to Christians, even Protestants, excluding Catholics (foreign power agents) and atheists (untrustworthy oaths). He defends toleration while using anti-Papist rhetoric of the Country Party.

Locke’s toleration arguments link to his civil government theory. Civil interests are life, liberty, health, property, magistrate/government’s proper concern, using force to protect them. Salvation is outside civil interests, beyond magistrate’s legitimate concern. Locke adds a right to natural rights: freedom to choose salvation path. (See Toleration in Locke’s Political Philosophy entry.)

State force to impose beliefs or practices is illegitimate and ineffective for belief change. Forcing profession of belief is hypocritical:

A sweet religion, indeed, that obliges men to dissemble, and tell lies to both God and man, for the salvation of their souls! If the magistrate thinks to save men thus, he seems to understand little of the way of salvation; and if he does it not in order to save them, why is he so solicitous of the articles of faith as to enact them by a law? (Mendus 1991: 41)

State religious persecution is inappropriate. “Locke holds that “Whatever is lawful in the commonwealth cannot be prohibited by the magistrate in the church”.” Even bread and wine use or calf sacrifice couldn’t be prohibited.

Competing churches raise the question of which should have power. The true church, not heretical ones, should have power. But Locke argues every church believes itself true, and only God judges. Religious knowledge skepticism is central to Locke‘s toleration argument.

Bibliography

Primary Sources

Locke’s Works

Oxford University Press is producing a new edition of Locke’s works, superseding the 1823 Works of John Locke. The Clarendon editions, starting with Nidditch’s 1975 Essay Concerning Human Understanding, include Lovelace collection materials donated to Oxford by Paul Mellon, inherited from Locke’s nephew Peter King. This collection offers scholars better insights into Locke’s philosophical development.

• The Clarendon Edition of the Works of John Locke, Oxford: Clarendon Press:
  • [N] An Essay Concerning Human Understanding, Peter H. Nidditch (ed.), 1975. doi:10.1093/actrade/9780198243861.book.1
  • Some Thoughts Concerning Education, John W. Yolton and Jean S. Yolton (eds.), 1989. doi:10.1093/actrade/9780198245827.book.1
  • Drafts for the Essay Concerning Human Understanding, and Other Philosophical Writings: In Three Volumes, Vol. 1: Drafts A and B, Peter H. Nidditch and G. A. J. Rogers (eds.), 1990. doi:10.1093/actrade/9780198245452.book.1
  • The Reasonableness of Christianity: As Delivered in the Scriptures, John C. Higgins-Biddle (ed.), 2000. doi:10.1093/actrade/9780198245254.book.1
  • An Essay Concerning Toleration: And Other Writings on Law and Politics, 1667–1683, J. R. Milton and Philip Milton (eds.), 2006. doi:10.1093/actrade/9780199575732.book.1
  • Vindications of the Reasonableness of Christianity, Victor Nuovo (ed.), 2012. doi:10.1093/actrade/9780199286553.book.1
  • A Paraphrase and Notes on the Epistles of St Paul to the Galatians, 1 and 2 Corinthians, Romans, Ephesians, 2 volumes, Arthur W. Wainwright (ed.)
    • volume 1, 1987. doi:10.1093/actrade/9780198248019.book.1
    • volume 2, 1987. doi:10.1093/actrade/9780198248064.book.1
  • Locke on Money, 2 volumes, Patrick Hyde Kelly (ed.)
    • Volume 1, 1991. doi:10.1093/actrade/9780198245469.book.1
    • Volume 2, 1991,. doi:10.1093/actrade/9780198248378.book.1
  • The Correspondence of John Locke, eight volumes, E.S. de Beer (ed.)
    • Vol. 1: Introduction; Letters Nos. 1–461, 2010. doi:10.1093/actrade/9780199573615.book.1
    • Vol. 2: Letters Nos. 462–848, 1976. doi:10.1093/actrade/9780198245599.book.1
    • Vol. 3: Letters Nos. 849–1241, 1978. doi:10.1093/actrade/9780198245605.book.1
    • Vol. 4: Letters Nos. 1242–1701, 1978. doi:10.1093/actrade/9780198245612.book.1
    • Vol. 5: Letters Nos. 1702–2198, 1979. doi:10.1093/actrade/9780198245629.book.1
    • Vol. 6: Letters Nos. 2199–2664, 1980. doi:10.1093/actrade/9780198245636.book.1
    • Vol. 7: Letters Nos. 2665–3286, 1981. doi:10.1093/actrade/9780198245643.book.1
    • Vol. 8: Letters Nos. 3287–3648, 1989. doi:10.1093/actrade/9780198245650.book.1

Other notable editions:

• An Early Draft of Locke’s Essay, Together with Excerpts from his Journal, Richard I. Aaron and Jocelyn Gibb (eds.), Oxford: Clarendon Press, 1936.
• John Locke, Two Tracts of Government, Phillip Abrams (ed.), Cambridge: Cambridge University Press, 1967.
• Locke’s The Two Treatises of Civil Government, Richard Ashcraft (ed.), London: Routledge, 1987.
• [Axtell 1968], The Educational Writings of John Locke: A Critical Edition, James L. Axtell (ed.), Cambridge: Cambridge University Press.
• [Gay 1964], John Locke on Education, Peter Gay (ed.), New York: Bureau of Publications, Columbia Teachers College, 1964.
• Epistola de Tolerantia: A Letter on Toleration, Latin text edited with a preface by Raymond Klibansky; English translation with an introduction and notes by J. W. Gough, Oxford: Oxford University Press, 1968.
• [G&T 1996] “Some Thoughts Concerning Education” and “The Conduct of the Understanding”, Ruth W. Grant and Nathan Tarcov (eds), Indianapolis: Hackett Publishing Co., 1996.
• [Laslett 1960] Locke’s Two Treatises of Government, Peter Laslett (ed.), Cambridge: Cambridge University Press, 1960.
• [Woozley 1964], An Essay Concerning Human Understanding, abridged, A.D. Woozley (ed.), London: Fontana Library, 1964.

Other Primary Sources

• Boyle, Robert, 1675 [1979], “Some Physico-Theological Considerations About the Possibility of the Resurrection”, in Selected Philosophical Papers of Robert Boyle, M.A. Stewart (ed.), New York: Manchester University Press.
• Mill, John Stuart, 1843, A System of Logic Ratiocinative and Inductive, London: John W. Parker.

Secondary Sources

Biographies

• King, Lord Peter, 1991, The Life of John Locke: with extracts from his correspondence, journals, and common-place books, Bristol: Thoemmes.
• Fox Bourne, H.R., 1876, Life of John Locke, 2 volumes, New York: Harper & Brothers. Reprinted Scientia Aalen, 1969.
• Cranston, Maurice, 1957, John Locke, A Biography, reprinted Oxford: Oxford University Press, 1985.
• Woolhouse, Roger, 2007, Locke: A Biography, Cambridge: Cambridge University Press.

Books and Articles

• Aaron, Richard, 1937, John Locke, Oxford: Oxford University Press.
• Aarsleff, Hans, 1982, From Locke to Saussure: Essays on the Study of Language and Intellectual History, Minneapolis: University of Minnesota Press.
• –––, 1994 “Locke’s Influence”, in Vere Chappell (ed.), The Cambridge Companion to Locke, Cambridge: Cambridge University Press, pp. 252–289. doi:10.1017/CCOL0521383714.011
• Alexander, Peter, 1985, Ideas Qualities and Corpuscles: Locke and Boyle on the External World, Cambridge: Cambridge University Press.
• Alston, William and Jonathan Bennett, 1988, “Locke on People and Substances”, The Philosophical Review, 97(1): 25–46. doi:10.2307/2185098
• Anstey, Peter R., 2011, John Locke and Natural Philosophy, Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199589777.001.0001
• Armitage, David, 2004, “John Locke, Carolina and the Two Treatises of Government”, Political Theory, 32(5): 602–27. doi:10.1177/0090591704267122
• Arneil, Barbara, 1996, John Locke and America, Oxford: Clarendon Press.
• Ashcraft, Richard, 1986, Revolutionary Politics and Locke’s Two Treatises of Civil Government, Princeton: Princeton University Press.
• –––, 1992, “Latitudinarianism and Toleration: Historical Myth versus Political History”, in Kroll, Ashcraft, and Zagorin 1992: 151–177. doi:10.1017/CBO9780511896231.008
• Ayers, Michael, 1991, Locke: Epistemology and Ontology, 2 volumes, London: Routledge.
• Barresi, John, and Raymond Martin, 2000, Naturalization of the Soul: Self and Personal Identity in the 18th Century, London: Routledge.
• Bennett, Jonathan, 1971, Locke, Berkeley, Hume: Central Themes, Oxford: Oxford University Press.
• Bolton, Martha Brandt, 2004, “Locke on the Semantic and Epistemic Role of Simple Ideas of Sensation”, Pacific Philosophical Quarterly, 85(3): 301–321. doi:10.1111/j.1468-0114.2004.00200.x
• Brandt, Reinhard (ed.), 1981, John Locke: Symposium Wolfenbuttel 1979, Berlin: de Gruyter.
• Brewer, Holly, 2017, “Slavery, Sovereignty, and ‘Inheritable Blood’: Reconsidering John Locke and the Origins of American Slavery”, The American Historical Review, 122(4): 1038–1078. doi:10.1093/ahr/122.4.1038
• Chappell, Vere, 1992, Essays on Early Modern Philosophy, John Locke—Theory of Knowledge, London: Garland Publishing, Inc.
• –––, 1994, The Cambridge Companion to Locke, Cambridge: Cambridge University Press.
• –––, 2004a, “Symposium: Locke and the Veil of Perception: Preface”, Pacific Philosophical Quarterly, 85(3): 243–244. doi:10.1111/j.1468-0114.2004.00196.x
• –––, 2004b, “Comments”, Pacific Philosophical Quarterly, 85(3): 338–355. doi:10.1111/j.1468-0114.2004.00202.x
• Chomsky, Noam, 1966, Cartesian Linguistics: A Chapter in the History of Rationalist Thought, New York: Harper & Row.
• Dunn, John, 1969, The Political Thought of John Locke, Cambridge: Cambridge University Press.
• Farr, James, 2008, “Locke, Natural Law and New World Slavery”, Political Theory, 36(4): 495–522. doi:10.1177/0090591708317899
• Fox, Christopher, 1988, Locke and the Scriblerians, Berkeley: University of California Press.
• Garrett, Don, 2003, “Locke on Personal Identity, Consciousness and ‘Fatal Errors’”, Philosophical Topics, 31: 95–125. doi:10.5840/philtopics2003311/214
• Geach, Peter, 1967, “Identity”, The Review of Metaphysics, 21(1): 3–12.
• Gibson, James, 1968, Locke’s Theory of Knowledge and its Historical Relations, Cambridge: Cambridge University Press.
• Gordon-Roth, Jessica, 2015, “Locke’s Place-Time-Kind Principle”, Philosophy Compass, 10(4): 264–274. doi:10.1111/phc3.12217
• Grant, Ruth, 1987, John Locke’s Liberalism, Chicago: University of Chicago Press.
• Gaukroger, Stephen, 2010, The Collapse of Mechanism and the Rise of Sensibility: Science and the Shaping of Modernity 1680–1760, Oxford, Clarendon Press.
• Kretzmann, Norman, 1968, “The Main Thesis of Locke’s Semantic Theory”, The Philosophical Review, 77(2): 175–196. Reprinted in Tipton 1977: 123–140. doi:10.2307/2183319
• Kroll, Peter, Richard Ashcraft, and Peter Zagorin (eds), 1992, Philosophy, Science and Religion in England 1640–1700, Cambridge: Cambridge University Press. doi:10.1017/CBO9780511896231
• Jolley, Nicholas, 1984, Leibniz and Locke, Oxford: Oxford University Press.
• –––, 1999, Locke, His Philosophical Thought, Oxford: Oxford University Press.
• –––, 2015, Locke’s Touchy Subjects: Materialism and Immortality, Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780198737094.001.0001
• Laslett, Peter, 1954 [1990], “John Locke as Founder of the Board of Trade”, The Listener, 52(1342): 856–857. Reprinted in J.S. Yolton 1990: 127–136.
• Lennon, Thomas M., 2004, “Through a Glass Darkly: More on Locke’s Logic of Ideas”, Pacific Philosophical Quarterly, 85(3): 322–337. doi:10.1111/j.1468-0114.2004.00203.x
• LoLordo, Antonia, 2010, “Person, Substance, Mode and ‘the moral Man’ in Locke’s Philosophy”, Canadian Journal Of Philosophy, 40(4); 643–668. doi:10.1080/00455091.2010.10716738
• Lott, Tommy, 1998, Subjugation and Bondage: Critical Essays on Slavery and Social Philosophy, New York: Rowman and Littlefield Publishers Inc.
• Lovejoy, Arthur O., 1936, The Great Chain of Being; a Study of the History of an Idea, Cambridge, MA: Harvard University Press.
• Lowe, E.J., 1995, Locke on Human Understanding, London: Routledge Publishing Co.
• Mackie, J. L. 1976, Problems from Locke, Oxford: Clarendon Press.
• Macpherson, C.B., 1962, The Political Theory of Possessive Individualism, Oxford: Oxford University Press.
• Mandelbaum, Maurice, 1966, Philosophy, Science and Sense Perception: Historical and Critical Studies, Baltimore: The John Hopkins University Press.
• Marshall, John, 2006, John Locke, Toleration and Early Enlightenment Culture, Cambridge UK, Cambridge University Press.
• Martin, C. B. and D. M. Armstrong (eds.), 1968, Locke and Berkeley: A Collection of Critical Essays, New York: Anchor Books.
• Mattern, Ruth, 1980, “Moral Science and the Concept of Persons in Locke”, The Philosophical Review, 89(1): 24–45. doi:10.2307/2184862
• McCann, Edwin, 1987, “Locke on Identity, Life, Matter and Consciousness” Archiv für Geschichte der Philosophie, 69(1): 54–77. doi:10.1515/agph.1987.69.1.54
• McLachlan, Hugh, 1941, Religious Opinions of Milton, Locke and Newton, Manchester: Manchester University Press.
• Mendus, Susan, 1991, Locke on Toleration in Focus, London: Routledge.
• Newman, Lex, 2004, “Locke on Sensitive Knowledge and the Veil of Perception—Four Misconceptions”, Pacific Philosophical Quarterly, 85(3): 273–300. doi:10.1111/j.1468-0114.2004.00199.x
• Olsthoorn, Johan and Laurens van Apeldoorn, 2020, “‘This man is my property’: Slavery and political absolutism in Locke and the classical social contract tradition”, European Journal of Political Theory, 21(2): 253–275. doi:10.1177/1474885120911309
• Rogers, G.A. John, 2004, “Locke and the Objects of Perception”, Pacific Philosophical Quarterly, 85(3): 245–254. doi:10.1111/j.1468-0114.2004.00197.x
• Roper, John, April 2004, Conceiving Carolina: Proprietors, Planters and Plots 1662–1729, New York, Palgrave/Macmillan.
• Russell, Daniel, 2004, “Locke on Land and Labor”, Philosophical Studies, 117(1–2): 303–325. doi:10.1023/B:PHIL.0000014529.01097.20
• Schouls, Peter, 1992, Reasoned Freedom: John Locke and the Enlightenment, Ithaca, NY: Cornell University Press.
• Simmons, A. John, 1992, The Lockean Theory of Rights, Princeton: Princeton University Press.
• Soles, David, 1999, “Is Locke an Imagist?” The Locke Newsletter, 30: 17–66.
• Strawson, Galen, 2011, Locke on Personal Identity, Princeton: Princeton University Press.
• Stuart, Matthew, 2013, Locke’s Metaphysics, Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199645114.001.0001
• Thiel, Udo, 2011, The Early Modern Subject: Self-Consciousness and Personal Identity from Descartes to Hume, Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199542499.001.0001
• Tarcov, Nathan, 1984, Locke’s Education for Liberty, Chicago: The University of Chicago Press.
• Tipton, I.C. (ed.), 1977, Locke on Human Understanding: Selected Essays, Oxford: Oxford University Press.
• Tully, James, 1980, A Discourse on Property, Cambridge: Cambridge University Press.
• –––, 1993, An Approach to Political Philosophy: Locke in Contexts, Cambridge: Cambridge University Press.
• Uzgalis, William L., 1988, “The Anti-Essential Locke and Natural Kinds”, The Philosophical Quarterly, 38(152): 330–339. doi:10.2307/2220132
• –––, 1990, “Relative Identity and Locke’s Principle of Individuation”, History of Philosophy Quarterly, 7(3): 283–297.
• –––, 2007, Locke’s Essay Concerning Human Understanding—A Reader’s Guide, London: Continuum.
• –––, 2017, “John Locke, Racism, Slavery and Indian Lands”, in Naomi Zack (ed.), The Oxford Handbook to Philosophy and Race, Oxford: Oxford University Press.
• Walmsley, Jonathan and Waldman Felix, 2019 “John Locke and Toleration of Catholics: A New Manuscript”, Historical Journal, 62: 1093–1115. [Includes transcription of “Reasons for tolerating papists with others” St. Johns College, Annapolis, Maryland, Greenfield Library.]
• Wilson, Margaret Dauler, 1999, Ideas and Mechanism: Essays on Early Modern Philosophy, Princeton: Princeton University Press.
• Wilson, Thomas D., 2016, The Ashley Cooper Plan: The Founding of Carolina and the Origins of Southern Political Culture, Chapel Hill, NC: University of North Carolina Press.
• Wood, Neal, 1983, The Politics of Locke’s Philosophy, Berkeley: University of California Press.
• Woolhouse, R.S., 1971, Locke’s Philosophy of Science and Knowledge, New York: Barnes and Noble.
• –––, 1983, Locke, Minneapolis: University of Minnesota Press.
• –––, 1988, The Empiricists, Oxford: Oxford University Press.
• Yaffe, Gideon, 2000, Liberty Worth the Name: Locke on Free Agency, Princeton: Princeton University Press.
• –––, 2004, “Locke on Ideas of Substance and the Veil of Perception”, Pacific Philosophical Quarterly, 85(3): 252–272. doi:10.1111/j.1468-0114.2004.00198.x
• Yolton, Jean S., 1990, A Locke Miscellany, Bristol: Thoemmes Antiquarian Books.
• Yolton, John, 1956, John Locke and the Way of Ideas Oxford, Oxford University Press; reprinted, Bristol: Thoemmes Press, 1996.
• –––, 1969, John Locke: Problems and Perspectives: New Essays, Cambridge: Cambridge University Press.
• –––, 1970, John Locke and the Compass of Human Understanding, Cambridge: Cambridge University Press.
• –––, 1983, Thinking Matter: Materialism in Eighteenth Century Britain, Minneapolis: University of Minnesota Press.
• –––, 1984, Perceptual Acquaintance: From Descartes to Reid, Minneapolis: University of Minnesota Press.

Bibliographies

• Hall, Roland, and Roger Woolhouse, 1983, 80 Years of Locke Scholarship: A Bibliographical Guide, Edinburgh: University of Edinburgh Press.

Newsletter

Academic Tools

	How to cite this entry.
	Preview the PDF version of this entry at the Friends of the SEP Society.
	Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO).
	Enhanced bibliography for this entry at PhilPapers, with links to its database.

Other Internet Resources

Related Entries

Berkeley, George | Hume, David | Leibniz, Gottfried Wilhelm | liberalism | Locke, John: moral philosophy | Locke, John: on freedom | Locke, John: on personal identity | Locke, John: philosophy of science | Locke, John: political philosophy | Masham, Lady Damaris | personal identity | substance | tropes

Acknowledgments

The editors would like to thank Sally Ferguson for carefully proofreading the text.