Abstract

Although Brentano generally regarded himself as at heart a metaphysician, his work then and subsequently has always been dominated by the Psychology. He is rightly celebrated as the person who reintroduced the Aristotelian-Scholastic notion of intentio back into the study of the mind. Brentano's inspiration was Aristotle's theory of perception in De anima, though his terminology of intentional inexistence was medieval. For the history of the work and its position in his output may I refer to my Introduction to the reprinted English translation. Alongside Aristotle the work shows influences of Descartes, Comte and the British empiricists. The theory of intentionality presented in the Psychology is much less modern and less plausible than almost all recent commentary would have it, and was in any case not where Brentano's main interest lay. Intentionality simply served to demarcate mental phenomena from physical, in Book One, but the main aim was a classification of the mental, outlined in Book Two. Books Three to Five were to have dealt in detail with the three main classes of presentations, judgements and feelings, with the final book considering the metaphysics: mind-body and the immortality of the soul. Brentano's shifting views, recently documented in English with Benito Muller's translation of Descriptive Psychology, a work from the transitional 1890s, made the original plan obsolete. The role of an a priori, philosophical or descriptive psychology, methodologically prior to empirical-experimental genetic psychology, foreshadowed and influenced Husserl's notion of phenomenology, and Brentano's Comtean methodological epoche of desisting from controversial metaphysical statements in favour of an examination of the phenomena likewise presaged Husserl's more ponderous phenomenological reductions. Brentano's other work covers most areas of philosophy, notably ethics, where he upheld a form of a priori intuitionism much admired by G. E. Moore, the philosophy of religion, metaphysics, philosophy of language, deductive and inductive logic, and the history of philosophy. I shall mention just two areas. In his logic lectures from 1866 onwards (a compilation published 1956) Brentano rejected the subject-predicate analysis of simple judgements and proposed instead (for which he apparently secured written assent from Mill) that all judgements are logical compounds of positive and negative existential judgements. For example the universal judgement All men are mortal becomes the negative existential There are no immortal men. On this basis Brentano radically simplified the inference rules of deductive logic. While unlike de Morgan, Frege and others he does not go beyond logic's traditional scope by recognising relations, within its bounds his reformed-term logic is simple, elegant and easily teachable. Some of his ideas in logic influenced the young Husserl. Unfortunately Brentano took against mathematical logic, which he wrongly associated exclusively with Hamilton's confused doctrine of the quantification of the predicate. His inductive logic, which takes up by far the greater part of his logic lectures, remains unresearched to this day.