Acts and Dispositions in John Buridan’s Faculty Psychology

Abstract

John Buridan (ca. 1300–1361) uses the concepts of actus and habitus in his psychology to explain the difference between actual or occurrent thoughts and the dispositions to think those same thoughts. But since mental qualities are immaterial, Buridan must finesse his account of material qualities to save the psychological phenomena. He argues that thoughts and dispositions are really distinct from the human soul and from each other, and that because a thought and its corresponding disposition are different kinds of quality, we cannot say that they differ merely in terms of intensity. This leaves him with the unresolved problem of explaining how one kind of psychological quality can be caused by another that is qualitatively distinct from it.