I’m working on my second draft of Key Terms in Philosophy of Mind, a book under contract with Continuum Books. From time to time I’ll be posting draft entries on Brain Hammer, especially for controversial or especially difficult to arrive at definitions. (See also my Philosophy of Mind MetaResource.) Here’s “introspection”:
introspection, the faculty by which the mind is known to itself without the KNOWLEDGE in question being the consequence of an INFERENCE. Introspection shares with PERCEPTION the feature of being a means to non-inferential knowledge, but differs from perception in providing non-inferential knowledge about the mind. Despite this key difference between introspection and perception, some philosophers hold that introspection is sufficiently similar to perception to be regarded as a faculty of inner-sense. Against the view that introspection is a kind of perceptual faculty is the following consideration. In the sensory perception of, for instance, a red square, there arises a sensory intermediary between my AWARENESS of the square as red and the red square itself: this intermediary is a SENSATION, in this case a sensation of redness (and perhaps also a sensation of square-ness). The presence of a sensation is what makes this awareness a sensory perception as opposed to a mere THOUGHT or BELIEF that a red square is present. By analogy, if introspection is sensory as opposed to merely a kind of thought or belief, then it would be natural to supposed that when introspecting a sensation itself, there should be an additional intermediary, this time a sensation of the sensation. However, many philosophers find implausible the suggestion that there are such higher-order sensations, that is, sensations of sensations. A different kind of position to hold about the introspection of perceptual states is that not only does introspection fail to reveal any sensations of sensations (higher-order sensations), we are incapable being introspectively aware of even first-order sensations. For more on this view, see TRANSPARENCY (OF EXPERIENCE).
Another set of controversies surrounding introspection involve those outlined in the entry on FIRST-PERSON AUTHORITY concerning whether introspective beliefs have an epistemological (see EPISTEMOLOGY) status or level of justification superior to non-introspective beliefs.