Although Buridan remained the predominant figure in logic, Albert's Perutilis logica (c. 1360) was destined to serve as a popular text because of its systematic nature and also because it takes up and develops essential aspects of the Ockhamist position. Albert accepted Ockham's conception of the nature of a sign. Albert believed that signification rests on a referential relation of the sign to the individual thing, and that the spoken sign depends for its signification on the conceptual sign. Albert followed Ockham in his conception of universals and in his theory of supposition. Specifically, Albert preserved Ockham's notion of simple supposition, understood as the direct reference of a term to the concept on which it depends when it signifies an extra-mental thing. Albert followed Ockham in his theory of categories and contrary to Buridan, refused to treat quantity as a feature of reality in its own right, but rather reduced it to a disposition of substance and quality. Albert established signification through a referential relation to a singular thing defining the relation of the spoken to conceptual signs as a relation of subordination. Albert's treatment of relation was highly original. Although, like Ockham, he refused to construe relations as things distinct from absolute entities, he clearly ascribed them to an act of the soul by which absolute entities are compared and placed in relation to each other. He therefore completely rejected certain propositions Ockham had admitted reasonable, even if he did not construe them in the same way.