It is an ancient view, to be found even in Aristotle’s analysis of friendship, that the other is an alter ego, another myself. More recently, this conception has provoked spirited debate within and without the phenomenological tradition. It can be found in a wide variety of texts, from Husserl’s Cartesian Meditations to Thomas Nagel’s “What is it like to be a bat?” The basic position can be summarized as follows. Intentional experiences are subjective, first-person experiences, not objective, third-person experiences.

Written in an outstandingly clear and lively style, this 1969 book provokes its readers to rethink issues they may have regarded as long since settled.