De Anima & Parva Naturalia by Aristotle

Aristotle’s theories regarding the structure and functions of the soul are found chiefly in the De Anima and the tractates collectively known as the Parva Naturalia. These works belong to that part of the corpus which deals with what Aristotle understands by physics, or the world of corporeal substances. To Aristotle, the word soul is synonymous with the word life. Accordingly, the higher phenomena of mental life are among its vital activities.