An Enquiry Concerning Human Understanding is a book by the Scottish empiricist philosopher David Hume, published in English in 1748 under the title Philosophical Essays Concerning Human Understanding until a 1757 edition came up with the now-familiar name.Thomas Edmund Jessop, A Bibliography of David Hume and of Scottish Philosophy from Francis Hutcheson to Lord Balfour, 1966, pp.12--20.See via Google Books It was a revision of an earlier effort, Hume's A Treatise of Human Nature, published anonymously in London in 1739–40. Hume was disappointed with the reception of the Treatise, which "fell dead-born from the press,"Hume, David (1776), My Own Life, Appendix A of Ernest Campbell Mossner, The Life of David Hume, University of Texas Press, 1954. as he put it, and so tried again to disseminate his more developed ideas to the public by writing a shorter and more polemical work.
The end product of his labours was the Enquiry. The Enquiry dispensed with much of the material from the Treatise, in favour of clarifying and emphasizing its most important aspects. For example, Hume's views on personal identity do not appear. However, more vital propositions, such as Hume's argument for the role of habit in a theory of knowledge, are retained.
This book has proven highly influential, both in the years that would immediately follow and today. Immanuel Kant points to it as the book which woke him from his self-described "dogmatic slumber."I. Kant "Prolegomena to Any Future Metaphysics" The Enquiry is widely regarded as a classic in modern philosophical literature.
Content The argument of the Enquiry proceeds by a series of incremental steps, separated into chapters which logically succeed one another. After expounding his epistemology, Hume explains how to apply his principles to specific topics.
1. Of the different species of philosophy In the first section of the Enquiry, Hume provides a rough introduction to philosophy as a whole. For Hume, philosophy can be split into two general parts: natural philosophy and the philosophy of human nature (or, as he calls it, "moral philosophy"). The latter investigates both actions and thoughts. He emphasizes in this section, by way of warning, that philosophers with nuanced thoughts will likely be cast aside in favor of those whose conclusions more intuitively match popular opinion. However, he insists, precision helps art and craft of all kinds, including the craft of philosophy.
2. Of the origin of ideas Next, Hume discusses the distinction between impressions and ideas. By "impressions", he means sensations, while by "ideas", he means memories and imaginings. According to Hume, the difference between the two is that ideas are less vivacious than impressions. For example, the idea of the taste of an orange is far inferior to the impression (or sensation) of actually eating one. Writing within the tradition of empiricism, he argues that impressions are the source of all ideas.
Hume accepts that ideas may be either the product of mere sensation or of the imagination working in conjunction with sensation.In Locke's terminology, this was known as the division between simple and complex ideas of sense. According to Hume, the creative faculty makes use of (at least) four mental operations that produce imaginings out of sense-impressions. These operations are compounding (or the addition of one idea onto another, such as a horn on a horse to create a unicorn); transposing (or the substitution of one part of a thing with the part from another, such as with the body of a man upon a horse to make a centaur); augmenting (as with the case of a giant, whose size has been augmented); and diminishing (as with Lilliputians, whose size has been diminished). (Hume 1974:317) In a later chapter, he also mentions the operations of mixing, separating, and dividing. (Hume 1974:340)
However, Hume admits that there is one objection to his account: the problem of "The Missing Shade of Blue". In this thought-experiment, he asks us to imagine a man who has experienced every shade of blue except for one (see Fig. 1). He predicts that this man will be able to divine the color of this particular shade of blue, despite the fact that he has never experienced it. This seems to pose a serious problem for the empirical account, though Hume brushes it aside as an exceptional case by stating that one may experience a novel idea that itself is derived from combinations of previous impressions. (Hume 1974:319)
3. Of the association of ideas In this chapter, Hume discusses how thoughts tend to come in sequences, as in trains of thought. He explains that there are at least three kinds of associations between ideas: resemblance, contiguity in space-time, and cause-and-effect. He argues that there must be some universal principle that must account for the various sorts of connections that exist between ideas. However, he does not immediately show what this principle might be. (Hume 1974:320-321)
4. Sceptical doubts concerning the operations of the understanding (in two parts) In the first part, Hume discusses how the objects of inquiry are either "relations of ideas" or "matters of fact", which is roughly the distinction between analytic and synthetic propositions. The former, he tells the reader, are proved by demonstration, while the latter are given through experience. (Hume 1974:322) In explaining how matters of fact are entirely a product of experience, he dismisses the notion that they may be arrived at through a priori reasoning. For Hume, every effect only follows its cause arbitrarily—they are entirely distinct from one another. (Hume 1974:324)
In part two, Hume inquires into how anyone can justifiably believe that experience yields any conclusions about the world:
"When it is asked, What is the nature of all our reasonings concerning matter of fact? the proper answer seems to be, that they are founded on the relation of cause and effect. When again it is asked, What is the foundation of all our reasonings and conclusions concerning that relation? it may be replied in one word, experience. But if we still carry on our sifting humor, and ask, What is the foundation of all conclusions from experience? this implies a new question, which may be of more difficult solution and explication." (Hume 1974:328)
He shows how a satisfying argument for the validity of experience can be based neither on demonstration (since "it implies no contradiction that the course of nature may change") nor experience (since that would be a circular argument). (Hume 1974:330-332) Here he is describing what would become known as the problem of induction.
5. Sceptical solution of these doubts (in two parts) According to Hume, we assume that experience tells us something about the world because of habit or custom, which human nature forces us to take seriously. This is also, presumably, the "principle" that organizes the connections between ideas. Indeed, one of the many famous passages of the Enquiry is on the topic of the incorrigibility of human custom. In Section XII, Of the academical or sceptical philosophy, Hume will argue,
"The great subverter of Pyrrhonism or the excessive principles of skepticism is action, and employment, and the occupations of common life. These principles may flourish and triumph in the schools; where it is, indeed, difficult, if not impossible, to refute them. But as soon as they leave the shade, and by the presence of the real objects, which actuate our passions and sentiments, are put in opposition to the more powerful principles of our nature, they vanish like smoke, and leave the most determined skeptic in the same condition as other mortals." (Hume 1974:425)
In the second part, he provides an account of beliefs. He explains that the difference between belief and fiction is that the former produces a certain feeling of confidence which the latter doesn't. (Hume 1974:340)
6. Of probability This short chapter begins with the notions of probability and chance. For him, "probability" means a higher chance of occurring, and brings about a higher degree of subjective expectation in the viewer. By "chance", he means all those particular comprehensible events which the viewer considers possible in accord with the viewer's experience. However, further experience takes these equal chances, and forces the imagination to observe that certain chances arise more frequently than others. These gentle forces upon the imagination cause the viewer to have strong beliefs in outcomes. This effect may be understood as another case of custom or habit taking past experience and using it to predict the future. (Hume 1974:346-348)
How to read Hume in contemporary terms (careful translation, not anachronism)
It's legitimate to read Hume as a precursor to subjective/epistemic probability (degrees of belief tied to evidence), but don't anachronistically import modern Bayesian formalism as if Hume provided it. Hume gives a qualitative, psychological account that makes room for quantitative comparisons of chances (e.g. dice examples). Practical takeaways for a scholar who wants to use Hume correctly
When citing Hume on induction, be explicit: he gives a psychological explanation and a skeptical challenge about justification, not a reductive proof that induction is irrational.
Distinguish the epistemic claim (we form beliefs by habit) from the metaphysical claim (there is or isn't a necessary connection in the world). Hume denies the epistemic access to metaphysical necessity, but does not deny the world's regularities.
Not: that probability = certainty. Hume explicitly says no degree of probability equals demonstrative certainty Not: that observed constant conjunction logically entails necessary connection. He denies that experience reveals metaphysical necessity; it only generates belief by association. Habit makes us expect the past to repeat; this expectation produces belief, not a rational proof. Hence the “problem of induction”: there is no rational justification (in Hume's argument) that induction is logically warranted. It is therefore rather surprising that the enormous attention which has been devoted to it over the years has not resulted in any general consensus as to how it should be interpreted, or, in consequence, how Hume himself should be seen. At one extreme is the traditional view, which takes the argument to be thoroughly sceptical, leading to the sweeping conclusion that all “probable reasoning” or “reasoning concerning matter of fact and existence” is utterly worthless, so that Hume is portrayed as a negative Pyrrhonian intent on undermining the credentials of all our would-be knowledge of the world. But at the other extreme a number of very prominent commentators, particularly in recent years, have put forward a strikingly contrasting view, that Hume's intentions here are entirely non-sceptical, and that so far from advancing a negative thesis himself, he is merely intent on showing the implausible consequences of the “rationalist” position taken by some of his philosophical opponents..."Millican Peter, Hume induction and probability, p17
7. Of the idea of necessary connection (in two parts)