ABSTRACT
This chapter explains the sense in which Ockham uses the term 'act' is an unfamiliar one for modern readers. It reviews the reasons which led him to drop the fictum-theory of concepts in favour of the actus-theory, and the reasons why he rejected the so-called species-theory, held in particular by Thomas Aquinas. The chapter explores how conceptual acts fit into human thought in Ockham's view. Realizing that the identification of the cognitive act with the concept amounts to identifying it with a sign of many singular things opens the way to seeing how it can still be a cognition of something without this something being either a fictum or a common nature: if conceptual acts are seen as general signs, only their singular significata are needed to serve as their objects. The intelligible species is not a substance of its own in Aquinas's view; nevertheless, it is not ontologically reducible to either the intellect or the cognitive acts and habitus.
