  Brentano also offered a quite general argument for reism based on the idea of intentionality as direction of thinking (and other mental acts). According to Brentano, the expression ‘to think’ is univocal in the sense that it always refers to a definite mental act directed to something. Accordingly ‘to think’ always means ‘to think of something’. This implies that the expression ‘something’ is univocal too, because there is no generic concept comprising both things and non-things as object to which intentional acts refer. This argument assumes that ‘something’ is co-extensional with ‘being’. Now, if ‘being’ is the most general noun, there is no noun which refers to being and non-being. Hence, if ‘something’ refers to a thing at time t, it cannot refer to a non-thing at different time. Although Brentano himself considered this argument as fully conclusive, it is dubious whether he was right in this respect.  His argument eventually implies that if ‘something’ refers to the objects a and b, both belong to the same ontological category, but not that they are things, at least, in any ordinary sense. Thus, Brentano’s argument for reism is at most an argument for a unicategorial ontology, that is, an ontology based on only one kind of object. See section 4 for the further discussion.