This book offers a concise exposition of the content theory of intentionality, which lies at the root of Husserl's phenomenology, for student and scholar. Originally published in 1982. The first part traces the history of phenomenology from its beginnings in Aristotle and Aquinas through Hume, Reid and the Brentano school to its first clear formulation in Frege and Husserl. Part two analyses some special problems involved in two important types of mental phenomena - perception and emotion - without abandoning the historical approach. Husserl's theory of perception is extensively discussed and a Husserlian analysis of so-called de re acts is attempted.