Epistemology

Hume's epistemology is quite unencumbered by skeptical worries about the existence of the physical world. However, Hume's philosophical preoccupations are shaped by a new kind of skepticism, which is most clearly expressed in the Enquiry concerning Human Understanding (1748).

For Hume, the problem of epistemology is justificatory: it must be established how people take themselves to have knowledge of the causal order of nature. For "nature," Hume remarks, "has kept us at a great distance from all of her secrets, and has afforded us only the knowledge of a few superficial qualities of objects; while she conceals from us those powers and principles, on which the influence of these objects entirely depends" (Enquiry, §4, p. 21).

The problem Hume identifies can be traced back to Locke, who noted that people do not have knowledge of the corpuscular microstructure of things (see Essay, book 4, chapter 3). They have knowledge only of the "nominal essence" of things; in other words, humans identify natural kinds on the basis of observable qualities that are constantly conjoined in experience, but since they cannot give an account of the corpuscular microstructure that allows them to observe these qualities, they do not have knowledge of the "real essence" of things. Hume generates a skeptical worry out of this: given that one has no cognitive access to the "secret nature" of things, then for all one knows this "secret nature" could change without any alteration in the observable properties of things. Hume recognizes that ordinary human cognitive practices carry on without people becoming encumbered by this skeptical worry. Yet "as a philosopher," he wonders: On what basis do we infer that the regular course of our experience should be a guide to determining a necessary connection of events observed in nature?

Hume responds to his "skeptical doubts" with a "skeptical solution" (Enquiry, §§4–5). People are able to make causal determinations only in a "subjective" fashion. In the course of experience, human minds are shaped by repetitions in circumstances. The result is the formation of tacit expectations, or anticipatory dispositions, which Hume calls "customs." These anticipatory dispositions are formed mechanically through associations of the imagination. The necessary connection thought in the concept of cause is merely something that "we feel in the mind, this customary transition of the imagination from one object to its usual attendant" (Enquiry, §7, p. 50). This "sentiment," Hume argues, is the source of the concept of causality. Thus Hume ends up with the following view. It cannot be said that one thing (A) brings about an effect in another thing (B); it may be said that representations of A are customarily conjoined with representations of B. Thus the necessity thought in the concept of cause is merely subjective: when faced with an event of type A, a subject cannot help but to anticipate an event of type B.