An Enquiry concerning Human Understanding

Contents

1. Section I Of the Different Species of Philosophy 25 min 10

   Hume contrasts two kinds of moral philosophy: the easy and popular, which paints virtue attractively and moves the reader to act, and the accurate and abstruse, which analyses the principles of the mind. The easy kind wins fame, but the abstruse serves it as anatomy serves painting, spreads accuracy through society, and alone can drive out the false metaphysics in which superstition shelters. A true metaphysics, a “mental geography” of the mind’s powers and perhaps its general principles, as Newton found the laws of the planets, is worth the effort. The book will try to join depth with clearness.

2. Section II Of the Origin of Ideas 12 min 7

   All perceptions are either impressions, the lively sensations and feelings, or ideas, their fainter copies in thought and memory. However free the imagination seems, it only combines and alters materials supplied by experience, and every simple idea is copied from an impression: analysis always traces ideas back to feelings, and those who lack a sense lack its ideas. Hume admits one exception, the missing shade of blue, and dismisses it as trivial. The principle gives a test for meaningless philosophical terms: ask from what impression the supposed idea is derived.

3. Section III Of the Association of Ideas 3 min 6

   Thoughts follow one another with a regularity visible even in dreams and wandering conversation, and the words of unconnected languages correspond, showing a universal principle at work. Hume reduces the connexions among ideas to three: resemblance, contiguity in time or place, and cause and effect. A picture leads to its original, one room to another, a wound to its pain. That the list is complete cannot be strictly proved, only made more probable by examining many instances.

4. Section IV Sceptical Doubts Concerning the Operations of the Understanding 33 min 8

   All objects of reason are either relations of ideas, known with certainty by thought alone, or matters of fact, whose contrary is always conceivable. Reasoning about matters of fact rests on cause and effect, and causes are never discovered a priori: Adam could not foresee that water would drown him, nor anyone how billiard balls will move. Part II asks what grounds conclusions from experience. Not demonstration, since a change in nature is conceivable; not probable argument, since that already assumes the future resembles the past. Infants and animals draw these inferences, so they cannot depend on reasoning.

5. Section V Sceptical Solution of These Doubts 30 min 8

   Academic scepticism threatens no practical harm, since nature will always prevail over argument. The principle that carries us from past to future is custom or habit, “the great guide of human life”, not reason. Belief differs from fiction not in its ideas but in a feeling of greater vividness and steadiness, produced when a present impression is joined by custom to a related idea. Resemblance and contiguity enliven ideas in the same way, as pictures, relics and nearness to home show. This instinct gives a kind of pre-established harmony between nature and our thoughts.

6. Section VI Of Probability 6 min 3

   Chance is only ignorance of real causes, but it shapes belief. When more sides of a die favour one result, the mind meets that result more often in running over the possibilities, and the concurrence of views strengthens belief in it. The probability of causes works the same way: where effects have varied, as with rhubarb, opium or January frost, we transfer the past to the future in proportion, and believe most firmly in the outcome most often observed.

7. Section VII Of the Idea of Necessary Connexion 38 min 13

   The ideas of power and necessary connexion are the most obscure in metaphysics, so Hume looks for the impressions they are copied from. External objects show only succession, never a binding force. Nor does the will give the impression: we do not know how mind moves body or summons ideas, and its limits are learned only by experience. The occasionalists’ appeal to God’s will only removes us further from experience. The idea comes instead from the mind’s customary transition after repeated conjunctions, and cause can be defined only by constant conjunction or by that transition.

8. Section VIII Of Liberty and Necessity 50 min 11

   Hume claims the old dispute over free will is merely verbal. Necessity, in matter as in mind, is nothing but constant conjunction and the inference it produces, and everyone relies on the regularity of human conduct in trade, politics, history and daily life. Liberty, properly defined, is the power to act or not according to the will, which all allow; liberty opposed to necessity would be mere chance. Part II argues that both doctrines are essential to morality and law, answers the charge that necessity makes God the author of sin only partly, and returns philosophy to common life.

9. Section IX Of the Reason of Animals 8 min 4

   Animals, like people, learn from experience: horses, greyhounds and dogs infer effects from causes. They cannot be following arguments that nature is uniform, so their inferences must rest on custom, and by analogy so do ours. Hume ends by calling experimental reasoning itself “a species of instinct”, which humans share with beasts.

10. Section X Of Miracles 47 min 22

    Hume’s famous argument against miracles. A wise man proportions belief to evidence, and testimony is trusted only because experience shows it usually true. A miracle violates laws established by uniform experience, so no testimony can establish one unless its falsehood would be more miraculous. Part II adds that no miracle has had adequate witnesses, that love of wonder and religious zeal corrupt testimony, that miracles flourish among the ignorant, and that rival religions’ miracles cancel out. Vespasian, Cardinal de Retz and the Abbé Pâris serve as test cases. Christianity, Hume ironically concludes, rests on faith, not reason.

11. Section XI Of a Particular Providence and of a Future State 36 min 10

    In a dialogue, a friend speaks as Epicurus before the Athenians. Granting the argument from design, he says we may ascribe to the gods only what their works display, and cannot infer a future state or rewards beyond the present course of nature. So his denial of providence cannot harm society. The narrator objects that belief in future rewards restrains people whatever its logic, but agrees that philosophy should be tolerated. He ends by doubting whether a unique cause of a unique effect can be inferred at all.

12. Section XII Of the Academical or Sceptical Philosophy 35 min 13

    Hume distinguishes Descartes’s antecedent doubt, which would be incurable, from scepticism that follows inquiry. Arguments against the senses, against abstract reasoning (infinite divisibility) and against inference from experience cannot be refuted, but Pyrrhonism cannot survive action and common life. What remains is a mitigated, academic scepticism: modesty in judgment and the restriction of inquiry to quantity and number or to matters of fact. Any book containing neither should be committed “to the flames”.