Abstract

Aristotle's argues in _DA_ II.2 that a proper causal definition of the soul is required if we are to know what it is. The attempt to identify the essence of the soul relies on a common conception of it as the cause of life. Since life is said in many ways, the definition of soul will be differentiated accordingly. This approach should be seen in the context of Aristotle's theory of demonstration, as articulated in the _APo_. The definition of the soul will provide the explanatory principles for demonstrations of the characteristic attributions of soul, and, by extension, of whatever attributes living beings have qua ensouled. In accordance with the _APo_'s view of demonstration in natural explanation, the soul's role in a demonstrative syllogism could be understood both as a formal, final, and efficient cause. The account of the soul in this way provides the explanatory basis for the biological works. The objections that have been raised against applying the model of demonstrative reasoning to the biological works do not count strongly against my interpretation of the _DA_.