I is perhaps the most important and the least understood of our everyday expressions. This is a constant source of philosophical confusion. Max de Gaynesford offers a remedy: he explains what this expression means, its logical form and its inferential role. He thereby shows the way to an understanding of how we express first-personal thinking. He dissolves various myths about how I refers, to the effect that it is a pure indexical. His central claim is that the key to understanding I is that it is the same kind of expression as the other singular personal pronouns, you and he/she: a deictic term, whose reference depends on making an individual salient. He addresses epistemological questions as well as semantic questions, and shows how they interrelate. The book thus not only resolves a key issue in philosophy of language, but promises to be of great use to people working on problems in other areas of philosophy.