Understand in about 6 minutes
Hume argues that all factual knowledge rests on experience, that causal belief comes from custom rather than reason, and that the wise mind proportions belief to evidence.
Idea map
Mental models
Trace any idea back to the impression it copies. If no impression can be produced, the idea is suspect and may be meaningless.
It offers a concrete check for empty or confused terms: demand the experience the concept is supposed to come from.
Repeated experience of two events together produces a habit that carries the mind from one to the other; this felt transition, not argument, is what belief actually is.
It explains why we confidently expect the future without being able to justify that expectation, separating psychological belief from logical proof.
Weigh the experience supporting and opposing a claim, and let the strength of belief follow the balance. Extraordinary claims require correspondingly stronger evidence.
It provides a rule for judging testimony and reports, including alleged miracles, by comparing competing improbabilities.
Summary
The Enquiry is Hume's attempt to bring careful, observational method to the study of the mind. He distinguishes an easy, ornamental philosophy from an exact one that tries to map the powers and limits of human understanding, and he sets out to do the harder work of tracing where our ideas come from and how far our reasoning can reach.
His starting point is that the contents of the mind divide into impressions, which are forceful and lively, and ideas, which are their fainter copies. From this he draws a test: every genuine idea must be derived from some prior impression. A blind person has no idea of colour, and a term that answers to no impression carries no clear meaning. This is Hume's instrument for clearing away confused or empty concepts.
Hume then divides all objects of reason into relations of ideas, such as the truths of mathematics, and matters of fact. Matters of fact rest on the relation of cause and effect, and here he presses his central problem. We never perceive any power or tie that binds cause to effect; we observe only that events have been constantly conjoined. Any inference from past experience to the future silently assumes that nature will continue uniform, and that assumption cannot be proved without already relying on it.
His solution is not to abandon such reasoning but to explain it differently. The principle that carries the mind from cause to effect is custom or habit, the great guide of human life. Belief is a livelier conception produced by repeated experience, not a conclusion forced by argument. The very idea of necessary connexion, he argues, arises only from the felt, customary transition of the mind from one object to its usual attendant.
Hume applies this empiricism to liberty and necessity, the reason of animals, and most controversially to miracles, where he argues that uniform experience is a full proof against any miraculous report, so that no testimony should be believed unless its falsehood would be more miraculous than the event. He closes by recommending a mitigated scepticism that confines enquiry to what experience can support, and would commit to the flames any volume containing neither abstract reasoning about quantity nor experimental reasoning about fact.
Key concepts
Selected Quotes
Custom, then, is the great guide of human life.
A wise man, therefore, proportions his belief to the evidence.
Commit it then to the flames: for it can contain nothing but sophistry
Source
Source text: Project Gutenberg edition of An Enquiry Concerning Human Understanding by David Hume.
HTML text: https://www.gutenberg.org/cache/epub/9662/pg9662.txt
Project Gutenberg states that this ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever.
Project Gutenberg reprints the posthumous edition of 1777, edited by L. A. Selby-Bigge; the work itself is an eighteenth-century original and no modern publication year is used here.