 Brentano introduces the notion of “reduction” at a linguistic level, applying it to sentences (or “propositions”), but what he is aiming at is a reduction at the level of mental phenomena. At the linguistic level, the claim is that any categorical proposition can be transformed without change of meaning into an existential proposition. At the level of judgement, the claim is that all judgements are in fact existential in character (and hence non-propositional). That shows for Brentano how language disguises the true nature of our judgements. When somebody asserts, for instance, that all S are P, he seems to make a positive judgement about all S. In fact, however, his judgement is negative and of the form “No S-that-is-not-P exists”. The point of the reduction thesis is to remove the linguistic disguise and to uncover the true form of our judgements. It also ensures that the judgements expressed by categorical and existential propositions are of the same kind. While such unification could also be achieved by saying that existential propositions express categorical judgement, Brentano’s thesis reverses that claim by declaring categorical propositions to express existential judgements.