 We already noted that Brentano’s Psychology is not just a book about mental phenomena. It also includes fundamental considerations pertaining to logic and epistemology. In that sense Brentano is no doubt a “psychologist”. He takes judgements to be the primary bearers of truth, he defines logical inferences as relations between judgements, and he considers validity to emerge from the evidence of our judgements about such relations. In taking this approach, Brentano sets himself apart from the rising “mathematical logic” (see PES Appendix x). Instead of applying mathematical tools in logic, Brentano believed that logic will advance better by applying the tools of descriptive psychology. To prove his case, Brentano sketches a reform of traditional logic based on his reduction thesis.