“All knowledge is either conception or assent”. On the history and significance of a fundamental distinction in Islamic philosophy

Following Aristotle, classical Islamic philosophers distinguished between two types of knowledge: conception and assent. This paper argues that the discussions elicited by this distinction are an essential feature of postclassical Islamic philosophy (ca. 1200–1800). The early postclassical philosophers made the distinction central to logic and thereby to epistemology and scientific inquiry at large. As the distinction came to be perceived as problematic, it sparked philosophical arguments about a range of issues in logic and epistemology. One particularly pertinent problem was the nature of the distinction itself: it was understood as an exclusive disjunction, but it seemed impossible to define one notion without recourse to the other. In the fourteenth century this led to the emergence of a new genre of philosophical writings exclusively dedicated to discussing the precise nature of the distinction. This paper discusses some of the central arguments of these writings, showing how philosophers grappling with that problem devised new theories of judgement and new forms of the proposition as they were continuously developing their theory of knowledge.