Tiril Johansen

This book offers an important study of Aristotle's theory of the sense-organs. It aims to answer two questions central to Aristotle's psychology and biology: why does Aristotle think we have sense-organs, and why does he describe the sense-organs in the way he does? The author looks at all the Aristotelian evidence for the five senses and shows how pervasively Aristotle's accounts of the sense-organs are motivated by his interest in form and function. The book also engages with the celebrated problem of whether perception for Aristotle requires material changes in the perceiver. It argues that, surprisingly to the modern philosopher, nothing in Aristotle's description of the sense-organs requires us to believe in such changes.

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.

At Timaeus 48e2–52d4 Timaeus sets out to establish that there are three principles or kinds underlying the creation of the cosmos, not just the two he acknowledged earlier. The way he does so is not simply by adding an account of the third kind to the accounts of being and becoming that he has already given. Rather he does so by showing how each of the three differs from the others. It has not been noticed how this procedure structures the receptacle passage. The passage divides up into three parts, each punctuated by a list of the three kinds in a significant order. If we take X, Y and Z to stand for ‘becoming’, ‘being’ and ‘receptacle’ ’ respectively, the structure is X≠Z, X≠Y, Y≠Z. By showing the distinctness of each pair, Timaeus demonstrates that all the kinds are distinct and that they are indeed three in number.