The term introspection might be defined as the direct, conscious examination or observation by a subject of his or her own mental processes. The term is derived from two Latin words, spicere ("to look") and intra ("within").

From at least the time of René Descartes up to the early twentieth century, it would have been considered unproblematic that the mind can reflect (or bend its attention back) upon itself. In the eighteenth and nineteenth centuries, if not earlier, self-reflection began to be interpreted, in the main, as introspection. In turn, to introspect one's own mental processes was explained in terms of the capacities (1) to focus the full glare of one's conscious attention upon the task of observing some particular, first-level, conscious process (or mental act), which was an item in one's stream of consciousness, and (2) to report in a privileged and incorrigible way upon the results of such...