RICCARDO MARTINELLI Descriptive Empiricism: Stumpf on Sensation and Presentation 1. Stumpf ’s empiricism The first book of David Hume’s Treatise of Human Nature opens with the following words: All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call IMPRESSIONS and IDEAS. The difference betwixt these consists in the degrees of force and liveli- ness, with which they strike upon the mind, and make their way into our thought or consciousness. (Hume (1739), 1) Hume believes that “it will not be very necessary to employ many words in explaining this distinction”. Notwithstanding some remarkable excep- tions, e.g. in dreaming or madness, the difference between the two species of human perception is quite clear. Impressions exhibit a typical “force and violence”: ideas, on the other hand, are the “faint images” of impres- sions, as they occur “in thinking and reasoning”. Hume’s entire empirical reconstruction and classification of mental phenomena is based on this distinction. Impressions and ideas, from his point of view, differ essen- tially in the specific degree of “force and liveliness”. As this example suggests, the relationship between sense impressions and ideas necessarily represent a capital issue for any kind of philosophical em- piricism. At least, this is certainly the case for Carl Stumpf. In the first place, Stumpf ’s philosophy is actually a peculiar form of empiricism, supporting his excellent experimental work in psychology. Along with a few analytical a priori logical truths, Stumpf recognised and appreciated synthetical a pos- teriori judgments as the main source of human knowledge (Stumpf (1939), 205). Secondly, this empiricism is bound to the assumption of a continuous gradual difference in intensity between “sensations” (Empfindungen) and “presentations” (Vorstellungen). Except for the lexical choice, Stumpf ap- pears to agree completely with the beginning of Hume’s Treatise. Brentano Studien 10  QG HGLWLRQ 2006), 81-100