The Essay Concerning Human Understanding is Locke's foundational work of modern empiricism — four books arguing against innate ideas and developing the doctrine that all knowledge derives from sensation and reflection.
essay-concerning-human-understanding
Locke's foundational work of modern empiricism, in four books, arguing against innate ideas and developing the doctrine that all knowledge derives from sensation and reflection.
First edition 1689 (dated 1690); four subsequent revised editions in Locke's lifetime, the last in 1700.
Introduction
The Essay Concerning Human Understanding is John Locke's foundational philosophical work and the founding text of modern empiricism. Across four books and approximately 270,000 words, it inquires into the original, certainty, and extent of human knowledge — the central question of modern epistemology. The Essay opens by attacking innate ideas, develops the empiricist doctrine that all knowledge derives from sensation and reflection, analyzes the categories of human cognition (substance, identity, mode, relation), and concludes with a careful demarcation of what we can and cannot reasonably claim to know.
The Essay shaped modern philosophy more profoundly than any single seventeenth-century work outside Descartes's Meditations. The British empiricist tradition through Berkeley and Hume, the Continental engagement (especially Leibniz's New Essays), and the Enlightenment epistemological tradition all developed in substantial dialogue with it.
Form, length, date, language
The Essay is a treatise in four books, totaling approximately 270,000 words in English. The first edition was published in late 1689 (dated 1690); four subsequent revised editions appeared in Locke's lifetime, the last in 1700. The original language is English in Locke's distinctively clear, conversational, sometimes prolix style.
Locke had been working on the Essay since 1671, when (he reports) a discussion among friends about the principles of morality and revealed religion had been brought up short by the recognition that they had no agreed account of human cognitive capacities. The Essay is the working out of that prior question.
Why it was written
The methodological premise of the Essay is that before we can responsibly ask what is true about the world, we should ask what the human mind is capable of knowing. The inquiry into cognitive capacities is the prerequisite for substantive philosophy and natural science alike. The Essay is therefore not a system of metaphysics in the rationalist style; it is a critical inquiry into the conditions of any possible metaphysics.
The broader project unifying the Essay with Locke's political and educational writings is the establishment of a moderate, evidence-based intellectual culture. The doctrine that the mind has no innate principles, that all knowledge comes from experience, that humans are equal in cognitive endowment, has political and pedagogical implications that Locke developed in parallel.
Structure and argument
Book I: Of Innate Notions. Sustained polemic against innate ideas. The targets are the Cartesians (and various Christian theologians) who held that certain ideas (the idea of God, the principles of mathematics, basic moral truths) are implanted in the mind at birth. Locke's central argument: if these ideas were innate, they would be universally present; but they are not universally present (children and the unschooled lack them); therefore they are not innate. The argument has been criticized as resting on a crude conception of what innateness would require, but its rhetorical effect was substantial.
Book II: Of Ideas. The positive account. The mind has no content at birth; everything in it comes from one of two sources: sensation (the outward senses providing ideas of external objects: color, sound, taste, smell, texture, shape, motion) and reflection (the mind's awareness of its own operations: perceiving, willing, doubting, judging). All ideas are either simple (received directly from sensation or reflection) or complex (constructed from simple ideas by the mind's faculty of combining, abstracting, and comparing).
Book II also develops the famous distinction between primary qualities (those that genuinely belong to objects: solidity, extension, figure, motion, number) and secondary qualities (those that exist only as the object's powers to produce ideas in us: color, sound, taste). The discussion of substance (II.23) is the foundation of Locke's empiricist suspicion of metaphysical posits: substance is the something, I know not what that we suppose underlies the observable properties.
Book II.27 develops the famous account of personal identity through continuity of consciousness, especially memory — the doctrine that has organized the modern philosophical literature on personal identity.
Book III: Of Words. Locke's philosophy of language. Words signify ideas in the mind of the speaker; communication works to the extent that the same words signify the same ideas. The book contains an extended treatment of the imperfections and abuses of language, and a famous nominalist discussion of general terms and essences (the real essence of a thing is its internal constitution, which we do not know; the nominal essence is the abstract idea the general term signifies).
Book IV: Of Knowledge and Opinion. Locke's mature account of knowledge. Knowledge is the perception of the agreement or disagreement of ideas. Three degrees: intuitive (immediate perception of agreement, as in white is not black), demonstrative (perception through a chain of intermediate ideas, as in mathematical demonstration), and sensitive (perception of the existence of external particular things, less certain than the previous two but adequate for practical life). The book closes with extensive treatment of the proper scope of inquiry, the distinction between knowledge and probable opinion, and the conditions under which faith can supplement reason.
Key passages
- I.ii.1–5 — the polemic against innate ideas.
- II.i.2 — the famous white paper (sometimes tabula rasa) characterization of the mind at birth.
- II.viii.9–10 — the distinction between primary and secondary qualities.
- II.xxiii.2 — substance as we know not what.
- II.xxvii — the famous chapter on personal identity through consciousness.
- III.iii.6–20 — the analysis of general terms and the nominal/real essence distinction.
- IV.i.2 — knowledge defined as the perception of the agreement or disagreement of ideas.
- IV.x — the demonstration of the existence of God.
- IV.xviii–xix — the relation between faith and reason.
Reception history
The Essay was a major intellectual event of the 1690s and went through four authorized editions in Locke's lifetime. It was rapidly translated into French (Coste, 1700) and Latin (Burridge, 1701) and engaged across Europe.
The most consequential immediate response was Leibniz's New Essays on Human Understanding (completed by 1704, published posthumously 1765), a paragraph-by-paragraph response defending innate ideas and the rationalist alternative. The work was held back from publication on Locke's death and only published when its philosophical significance was recognized in the eighteenth-century German rationalist tradition.
The British empiricist development through Berkeley and Hume was substantially shaped by the Essay. Berkeley's Principles of Human Knowledge (1710) accepted the empiricist starting point but rejected the distinction between primary and secondary qualities, arguing that all qualities exist only as ideas in minds. Hume's Treatise of Human Nature (1739) further radicalized the empiricist project. Kant's Critical philosophy is in part a response to the empiricist tradition the Essay founded.
The modern reception has been continuously active. The contemporary literature on personal identity remains substantially Lockean (Derek Parfit's Reasons and Persons, 1984). Recent work on the Essay (Vere Chappell, Michael Ayers, Edwin McCann) has restored serious engagement with the work's metaphysical and methodological commitments.
Contemporary engagement
The standard scholarly text is Peter Nidditch's Clarendon edition (1975); a more recent edition by Pauline Phemister (Oxford, 2008) is widely used pedagogically. Major recent scholarly work includes Michael Ayers's two-volume Locke (1991), Vere Chappell's Cambridge Companion to Locke (1994), Edwin McCann's chapter on Locke in the Cambridge History of Seventeenth-Century Philosophy, and the relevant essays in the Locke Studies journal. Active scholarly debates concern the relation between Locke's epistemology and his political philosophy, the interpretation of the primary/secondary quality distinction in light of contemporary philosophy of perception, the adequacy of the memory criterion of personal identity, and Locke's status as a representational versus direct realist about perception.
Further reading
- Locke — the author
- Empiricism — the tradition the work founded
- Hume — the philosopher who took the empiricist project to its limit
- Leibniz — the author of the major rationalist response
- Episteme — the cognitive achievement the Essay inquires into
- Belief Systems — the structure of belief the Essay analyzes
The founding text of modern empiricism. Four books inquiring into the original, certainty, and extent of human knowledge.