Todd Ganson

Aristotle’s philosophy of mind is often understood as anticipating present-day functionalist approaches to the mental. In Aristotle on the Sense-Organs Johansen argues at length that such interpretations of what Aristotle has to say about the senses are untenable. First, Aristotle does not allow that the matter of a sense-organ can be identified without reference to the form or function of the organ, so sense-organs are not compositionally plastic. Second, Aristotle’s conception of sense-perception is radically different from anything a philosopher today, functionalist or not, would find credible: acts of sense-perception on Aristotle’s view do not require material changes in the sense-organs. Developed carefully throughout all six chapters, Johansen’s defense of this latter claim is the most significant part of the book, and it will be my focus here.

Teleological accounts of sensory normativity treat normal functioning for a species as a standard: sensory error involves departure from normal functioning for the species, i.e. sensory malfunction. Straightforward reflection on sensory trade-offs reveals that normal functioning for a species can exhibit failures of accuracy. Acknowledging these failures of accuracy is central to understanding the adaptations of a species. To make room for these errors we have to go beyond the teleological framework and invoke the notion of an ideal observer from vision science. The notion of an ideal observer also sheds light on the important distinction between sensory malfunction and sensory limitation.