 With respect to the exact ontological status of such conceptual entities, however, Ockham changed his view over the course of his career. To begin with, he adopted what is known as the fictum-theory, a theory according to which universals have no “real” existence at all in the Aristotelian categories, but instead are purely “intentional objects” with a special mode of existence; they have only a kind of “thought”-reality. Eventually, however, Ockham came to think this intentional realm of “fictive” entities was not needed, and by the time of his Summa of Logic and the Quodlibets adopts instead a so called intellectio-theory, according to which a universal concept is just the act of thinking about several objects at once; metaphysically such an “act” is a singular quality of an individual mind, and is “universal” only in the sense of being a mental sign of several things at once and being predicable of them in mental  propositions.[32]