This paper offers both a phenomenologically psychological and phenomenologically transcendental account of the constitution of the unconscious. Its phenomenologically psychological portion is published here as Part I, while its phenomenologically transcendental portion will be published in the next volume of this journal as Part II. Part I first clarifies the issues involved in Husserl's differentiation of the respective contents and methodologies of psychological and transcendental phenomenology. On the basis of this clarification I show that, in marked contrast to the prevailing approach to the unconscious in the phenomenological literature, an approach that focuses on the emotive and aesthetic factors (rooted in Freud's theory of repression) in the descriptive account of the constitution of an unconscious, there are cognitive factors (rooted in Jung's theory of apperception) that have yet to be descriptively accounted for by phenomenological psychology. Part I concludes with a phenomenologically psychological account of the role these cognitive factors play in the constitution of an unconscious. Part II will show how Jung's claims regarding a dimension of unconscious contents that lacks genealogical links to consciousness proper, that is, the "collective unconscious, " can be phenomenologically accounted for if (1) Jung's methodological differentiation of empirical and interpretative (hermeneutically phenomenological) approaches to the unconscious is attended to and (2) such attention is guided by the phenomenologically transcendental critique of the emotive and aesthetic limitations of both the Freudian and heretofore Husserlian accounts of the descriptive genesis of something like an unconscious.