For Locke and Hume, and British empiricists generally, the way to understand any psychological concept is either to find it among the immediate data of introspection or to show how it is to be analyzed into such data. This approach ultimately stems from the Cartesian insistence that one knows one’s own states of consciousness better than anything else, in particular, better than physical objects and events, since it is possible to doubt the existence of all the latter but not all of the former.

William Alston, ‘Pleasure’, in Donald Borchert (ed.), The Encyclopedia of Philosophy, 2nd ed., 2006, Detroit, p. 622