Most accounts of self-knowledge begin from the idea that self-knowledge differs, in some profound way, from other types of empirical knowledge. The usual contrast is with perception (though there are other sources of empirical knowledge, such as memory). The acquaintance theory discussed in the previous chapter sees introspection as both metaphysically and epistemically special, as compared with perception. Rationalist views, to be discussed in the next chapter, claim that access to our own attitudes is conceptually guaranteed by our rational nature; by contrast, perceptual access to the external world is a contingent matter. Against this background, the inner sense theory is notable for emphasizing similarities between introspection and perception. Historically, the inner sense view is most closely associated with Locke

(see Section 2.4 above). Locke described introspection as an internal analogue of perception, a kind of internal sense.