 Etymologically, the term “introspection”—from the Latin “looking into”—suggests a perceptual or quasi-perceptual process. Locke writes that we have a faculty of “Perception of the Operation of our own Mind” which, “though it be not Sense, as having nothing to do with external Objects; yet it is very like it, and might properly enough be call’d internal Sense” (1690 [1975, 105], italics suppressed). Kant (1781/1997) says we have an “inner sense” by which we learn about mental aspects of ourselves that is in important ways parallel to the “outer sense” by which we learn about outer objects.