During his visit, Gary Hatfield pursued three topics. First, the crisis in psychology, in connection with the MPIWG workshop in October, 2008. The Gestalt psychologist Koffka used crisis talk during the 1920s and was joined by Koehler in the 1930s. They dated the crisis to the turn of century, and portrayed Wertheimer as responding to it by reintroducing meaning and significance into psychology, while continuing to pursue natural scientific methods. Koffka subsequently recounted that he changed his presentation of Gestalt psychology after emigrating to America, to downplay the emphasis on meaning. This claim does not withstand scrutiny—in practice, the Gestaltists offered no greater emphasis on meaning and significance prior to emigrating. The fact that Koffka made the statement reflects his perception of the tenor of American psychology.
The second topic concerns Descartes' account of the internal senses. Descartes acknowledged a more or less standard range of the internal senses, including imagination and memory. In the Aristotelian scheme, these had been assigned to the sensitive power of the soul. They included cognitive functions such as detecting remote harms (“harm” was not itself a quality perceived by the external senses). Such cognitive acts were not performed, in nonhuman animals, by the intellect, but by the powers of the sensitive soul. Descartes claimed to mechanize those powers (for both human and nonhuman animals). Because he accepted the Aristotelian topos of the internal senses, this meant he claimed to mechanize cognitive powers without connection to the mind. In the longer run, Gary Hatfield followed the reception of Cartesian mechanistic psychology in the eighteenth century for a book on Philosophy of Psychology for the Cambridge Evolution of Modern Philosophy Series.
The third topic concerned an image in Descartes' Dioptrique, which shows a partially dissected eye with a small human head peering at the back of it. This image has been interpreted in various ways: e.g., as implying that Descartes posited a homunculus in vision, or as a (perhaps unwitting) portrayal of the subject considering its own visual subjectivity. Gary Hatfield considered two classifications in examining diagrams of eye, mind, and cognitive processes, and of optical anatomy, especially before 1637 but also after.