Abstract

The immateriality of the intellect is central to Thomas Aquinas' philosophical anthropology because it forms the basis for his position that the human soul is an immaterial, intellectual substance that is incorruptible. It is noteworthy, then, that Aquinas' preferred argument for the immateriality of the intellect, which he derived from De anima 429a10-429b5, is out of favor with contemporary Thomists. I propose that part of the reason for this is that the wrong controlling text has been used. Although it has been neglected, Sentencia libri De anima III.1 is the best controlling text because it is Aquinas' lengthiest and clearest explanation of the argument; it illustrates how he derived the argument from the De anima; and it plays a pivotal role in the development of his understanding of the argument. ;Part I examines the argument in Sentencia libri De anima III.1. The study begins with the importance to Aquinas of William of Moerbeke's new translation of the De anima. Central to the dissertation is an analysis of Aquinas' presentation of the argument in the commentary. This makes it possible to discern the way in which Cajetan and more recent Thomists have misinterpreted the argument. Part II examines the argument in the context of Aquinas' other works. An inquiry into the development in his understanding of the argument reveals why he came to prefer it above all others. His preferred argument, which is based on all corporeal natures as the proper object of the human intellect, is compared to an argument that he came close to formulating but did not use based on the ultimate object of every intellect--ens intelligibile, or all being in its intelligibility. Since the latter involves the notion of infinity, the relationship of intellect, immateriality, and infinity in his philosophy is examined. The study concludes by noting the relative advantages of these two arguments, including their usefulness for Aquinas' time and for our own