Aristotelian Change and Scala Naturae

Aristotle famously distinguishes between three types of soul: the vegetative soul, the sensitive soul, and the intellective soul. However, the reason why Aristotle divides up the soul in this way is not so clear, and the existing literature on the matter is sparse and unconvincing. In this dissertation I explore the reasons why Aristotle distinguishes three types of soul based on his theory of natural change. I begin with an investigation into Aristotle’s argument concerning the principles of change, found in Physics I.5, where we see that all natural change requires contraries as principles of change. In that chapter I argue that to understand the mechanisms of a change in Aristotle’s natural philosophy we must understand the contraries at work in that change. Then I look at the fundamental contraries at work in interactions between non-living bodies (i.e. hot, cold, wet, and dry), and I show how the mechanisms of those changes are reducible to exchanges of these primary contraries. In chapter three I distinguish between the changes proper to the vegetative soul by showing how those changes are not reducible to the mechanisms at work in changes between non-living bodies, and how these changes allow for the transfer of matter without form. Chapter four argues that the changes proper to the sensitive soul differ from the vegetative soul because the sensitive faculties can receive forms without matter. In chapter five I show that the contraries of the intellect differ from the contraries of the sensitive soul by virtue of receiving universal forms rather than the particular forms of the sensitive faculties. In the end, we see that analyzing change through an analysis of contraries in change helps us to see why Aristotle divides up nature and the soul in the way he does.