An Enquiry concerning Human Understanding

Citation

Hume, D. (2008). An Enquiry concerning Human Understanding (P. Millican, Ed.). Oxford University Press (Oxford World's Classics).

Chapter Summary

The Enquiry is a short book of twelve numbered sections, some divided into Parts. The sections build on one another: Sections I to III prepare a theory of ideas, Sections IV to VII use it to examine reasoning about cause and effect, Section VIII applies the result to human action, Sections IX to XI turn to animals, miracles and religion, and Section XII asks how far scepticism can go. Before the text, the Oxford edition prints a long introduction by Peter Millican (pp. ix–lvi), a note on the text, a chronology and a select bibliography. The text itself begins on page 1, and the appendices start on page 133.

Section I: Of the Different Species of Philosophy

Hume distinguishes two ways of treating moral philosophy, or the science of human nature: the easy and obvious kind, which paints virtue in attractive colours, and the accurate and abstruse kind, which analyses the principles of human nature. He defends the second, arguing that careful enquiry can map the powers of the mind and, by showing the limits of the understanding, rid us of false metaphysics.

Section II: Of the Origin of Ideas

All perceptions of the mind are divided into forceful impressions and fainter ideas, which are copies of them. Hume argues that the mind only compounds materials given by sense and feeling, and proposes a test for any suspect term: ask which impression it is derived from. He notes one apparent exception, the missing shade of blue.

Section III: Of the Association of Ideas

Thoughts do not follow one another at random. Hume lists three principles of association: resemblance, contiguity in time or place, and cause and effect.

Section IV: Sceptical Doubts concerning the Operations of the Understanding

Part I separates the objects of human reason into relations of ideas, which can be discovered by thought alone, and matters of fact, which cannot, and argues that knowledge of cause and effect comes from experience, never from reasoning a priori. Part II asks what justifies the move from past experience to the future, and finds that every attempt to support it by argument assumes what is to be proved.

Section V: Sceptical Solution of these Doubts

Part I offers custom or habit as the principle that guides inference from experience, and treats it as a kind of instinct which nature has provided. Part II analyses belief as a more vivid, forceful and steady conception than mere imagination, produced by the principles of association.

Section VI: Of Probability

A short section on how a majority of chances produces belief, and on how the probability of causes involves the same process.

Section VII: Of the Idea of Necessary Connexion

Part I asks for the impression from which the idea of power or necessary connexion is copied, and rejects the suggestions that it comes from observing bodies, from the will's power over the body, or from the will's power over ideas; it also criticises appeals to God as the real cause of all things. Part II concludes that the idea comes from the habit of expecting the usual consequence after repeated conjunction, and offers two definitions of cause.

Section VIII: Of Liberty and Necessity

Hume holds that the old dispute over free will is largely verbal. The uniformity of human motives and actions is the same kind of regularity that we recognise in matter, and what we should call liberty is a power of acting according to the will. Part II argues that both necessity and liberty are needed for morality and ends by admitting that the problem of evil is a mystery philosophy cannot resolve.

Section IX: Of the Reason of Animals

Animals, like humans, learn from experience and draw inferences that can only rest on custom. Hume treats this as further support for his account of experimental reasoning as a form of instinct.

Section X: Of Miracles

Part I argues that belief should be proportioned to evidence, that a miracle is a violation of the laws of nature, and that uniform experience against it amounts to a proof. Part II gives reasons why testimony for miracles is weak and concludes that no testimony has established a miracle as the foundation of a system of religion.

Section XI: Of a Particular Providence and of a Future State

A conversation in which a speech attributed to Epicurus defends the harmlessness of denying providence and a future state. The reply is that from the world as an effect one cannot infer more in its cause than the effect shows, and the discussion tests this argument against the case of a unique universe.

Section XII: Of the Academical or Sceptical Philosophy

Part I examines the sceptical doubts about the senses and the objections to Cartesian doubt and to appeals to God's veracity. Part II considers sceptical objections to abstract and moral reasoning, and argues that a thoroughgoing Pyrrhonian cannot act on his principles. Part III recommends a mitigated scepticism that limits enquiry to subjects suited to the understanding, ending with the instruction to commit to the flames any volume that contains neither abstract reasoning about quantity or number nor experimental reasoning about fact.

Key Concepts

Sections I–III: Ideas

• Impressions and ideas: the more lively perceptions and their fainter copies.
• Association of ideas: resemblance, contiguity and cause and effect.

Sections IV–VII: Causation and Induction

• Relations of ideas and matters of fact: the two kinds of object of human enquiry.
• Custom or habit: the principle that carries the mind from one event to the expectation of its usual companion.
• Belief: a lively feeling attached to some conceptions, not a separate idea.
• Necessary connexion: the idea of power, which Hume traces to the felt transition after repeated conjunction.

Sections VIII–XII: Action, Religion and Scepticism

• Hypothetical liberty: the power of acting or not acting according to the will.
• Miracle: a violation of the laws of nature, evidence for which is weighed against uniform experience.
• Mitigated scepticism: the modest, cautious outlook that Hume contrasts with excessive scepticism.

Critical Analysis

Strengths

• A compact, sequential argument. The twelve sections, with the paragraph numbering of the standard text, allow a reader to follow one thread from the origin of ideas through causation to its consequences, with each section drawing on those before.
• Sharp statements of the central problems. The distinction between relations of ideas and matters of fact, the circularity of arguing from past to future, and the two definitions of cause are each stated within a few paragraphs.
• Wide range of application. The same principles are applied to free will, animal reason, testimony for miracles, natural religion and scepticism, which shows what an empiricist method can and cannot do.
• A well-equipped edition. Besides Millican's long introduction, the Oxford edition includes explanatory notes, a glossary, a glossarial index of philosophers and philosophical movements, indexes of themes and names, and appendices that include Hume's Abstract of the Treatise, his essay Of the Immortality of the Soul, excerpts from the Dialogues concerning Natural Religion and from his letters, and his autobiographical My Own Life.
• Complete text, not excerpts. Some courses read the Enquiry in an anthology that leaves sections out. The University of Florida course described below, for example, has to post Section XII on Canvas because it is omitted from the anthology the course uses, and adds extra paragraphs of Section I there as well. The Oxford edition prints all twelve sections, so it avoids this patchwork.

Limitations

• Compressed arguments. The Abstract of the Treatise printed in the appendix is a reminder that the Enquiry presents conclusions from a longer work in condensed form; on causation and the self a reader may want fuller versions.
• Narrow range. The Enquiry is concerned with the understanding; passion and moral theory belong to other works by Hume, so the volume does not give his ethics. Pomona's Fall 2024 Political Philosophy course assigns Hume on property and the original contract from the Treatise and Essays, rather than the Enquiry.
• Unresolved points. Section VIII ends by admitting that how God can cause all actions without being the author of moral evil is a mystery with which philosophy cannot deal, and Section XI is framed as a conversation with a friend in which Hume speaks through an imagined speech of Epicurus, so readers must separate Hume's own view from the positions he voices.
• Eighteenth-century idiom. Terms such as "moral reasoning" (reasoning about human affairs), "idea" and "philosophy" have different senses from modern usage, which is why the glossary and notes in an annotated edition are useful.

Where It Fits in the Course

The Enquiry is the empiricist counterpart to Descartes's Meditations in the modern philosophy course. Section XII, Part I answers Cartesian doubt directly: it argues that universal doubt, if taken seriously, cannot be cured and that appeal to God's veracity does not help. Reading the Meditations first makes this section much clearer. Garrett Thomson's Bacon to Kant and Anthony Gottlieb's The Dream of Enlightenment are good background reading for readers meeting the period for the first time, while Bennett's Learning from Six Philosophers has Hume among its six subjects, though its first volume covers Descartes, Spinoza and Leibniz. Kant's Critique of Pure Reason is the advanced work to come to later.

A recent survey course shows this placement in practice. The University of Florida modern philosophy course listed below gives the Enquiry a block of about eight meetings in March and early April, from 3 March to 2 April, reading it as one of the early modern texts collected in a single anthology.

How to Use This Book

This edition is for undergraduates in early modern philosophy, epistemology and philosophy of religion courses, and for independent readers; no knowledge of the period is needed.

A practical plan:

• Core: Sections I, II, IV, V, VII and XII; these contain the theory of ideas, the problem of induction and the account of causation and scepticism.
• Next: Sections VIII and X, which apply the core to free will and miracles and are often assigned on their own.
• Quick reads: Sections III, VI and IX are short.
• Optional: Section XI, which is a debate within a dialogue, and the appendices, especially the Abstract of the Treatise.
• Read Millican's introduction after a first pass through the text and use the explanatory notes and glossary to resolve unfamiliar terms.
• Cite by section and paragraph number.

Common course assignments

University of Florida, PHH 3400 Modern Philosophy, Spring 2025 (syllabus). This course does not use the Oxford edition. It assigns the Enquiry from Shapiro and Lascano's Early Modern Philosophy anthology (Broadview, 2022, ISBN 978-1554812790), cited below as EMP, with Canvas supplements for material the anthology leaves out. The page numbers below refer to that anthology, not to the Oxford edition.

Meeting	Date	Reading	Source
23	3/3	§ I	EMP 778–82, plus extra paragraphs on Canvas
24	3/10	§§ II–III	EMP 782–85
25	3/12	§ IV	EMP 785–91
26	3/14	§ V	EMP 791–98
27	3/24	§ IX; reread §§ IV–V	EMP 816–18
28	3/26	§ VII	EMP 799–807
29	3/28	§ XII (omitted from the anthology)	Canvas
31	4/2	§ VIII	EMP 807–16

Several features of this sequence are worth noting:

• Sections VI, X and XI do not appear on this schedule. The course concentrates on ideas, induction, causation, free will and scepticism, and leaves out probability, miracles and providence.
• Section IX on animal reason is taken out of numerical order. It is read straight after Sections IV–V, together with a reread of them, which treats it as support for the custom-based account of inference.
• Section VII follows that reread, and Section VIII comes last, after Section XII.

The UF path largely overlaps the "Core" plan above, adding Sections III, VIII and IX. A reader using the Oxford edition can follow the same order, using section numbers rather than page numbers. If you are preparing for a course that teaches miracles or philosophy of religion, add Sections X and XI yourself.

Edition and Sources

The edition listed here is the Oxford World's Classics text edited by Peter Millican. Readers who want a free text can use L. A. Selby-Bigge's second edition (1902) of the posthumous edition of 1777, available from Project Gutenberg, which keeps the same section structure and numbered paragraphs and adds an analytical index. The UF course above uses the Broadview Early Modern Philosophy anthology instead, so match its readings by section number.