The author offers an understanding of the psychoanalytic notion of the desire for knowledge and the possibility of attaining it as it finds expression in Freud's Leonardo da Vinci and a memory of his childhood. This understanding has not been explicitly articulated by Freud but may be considered integral to psychoanal ysis' Weltanschauung as shaped by Freud's legacy. It emerges through an attempt to explain basic shifts, contradictions, inconsistencies and tensions that become apparent from a close reading of the text of Leonardo. Articulating this implicit understanding of knowledge provides the grounds for a stance on epistemology that is integral to psychoanalysis and relevant to contemporary psychoanalytic concerns on this topic. This epistemology focuses on the necessary involvement of passion, rather than detachment, in the search for knowledge and views the psychoanalytic aim of self-knowledge as a derivative, and most immediate expression, of a broader and more basic human drive to know.