When my mother was three, her father came home one evening without his beard and she insisted he was Uncle Albert, my grandfather's younger and beardless brother. She thought he was, as usual, being a terrible tease, and she cried when he didn't admit his real identity. Only when he pulled out her daddy's silver pocket watch with its distinctive and beloved pop-up cover was she willing to be corrected. But just who was it that she had been thinking was being so mean, this man (her daddy) or Uncle Albert? This is what I mean by a confused idea.

I have an old letter from Yale's alumni association inquiring whether I, Mrs. Donald P. Shankweiler, knew of the whereabouts of their “alumnus” Ruth Garrett Millikan. This seemed a sensible question, I suppose, as according to their records we lived at the same address. Since I lived with myself, perhaps I knew where I was? By not owning up I evaded solicitations from Yale's alumni fund for a good many years.

More often, confusions about the identities of things are disruptive rather than amusing. It is fortunate that we generally manage recognition tasks so well, and our ability to do so deserves careful study. I will argue in this book that the most central job of cognition is the exceedingly difficult task of reidentifying individuals, properties, kinds, and so forth, through diverse media and under diverse conditions.