Philosophers and scientists of the Renaissance did not treat psychology, the philosophical study of the soul, as an independent discipline. Following the medieval tradition, they placed it within the broader context of natural philosophy, and they approached it, like the other sub-divisions of natural philosophy, through the works of Aristotle, notably De anima and the Parva naturalia. The term psychologia itself was coined–apparently by the German humanist Joannes Thomas Freigius in 1575 – to refer to the traditional complex of problems originating from these two works. Thus it is in relation to the Aristotelian tradition, and more specifically to the Aristotelian philosophy of nature, that the meaning and content of psychology in this period must be defined.

Aristotle and his followers defined the soul as the life principle of the individual body – that which differentiated living from non-living things. As such it was the source and formal cause of the specific functions and activities of animate beings, including plants and animals as well as men. Thus before the seventeenth century, when Descartes, Stahl and others moved to divorce the notions of life and soul, there was no clear division between psychology and what we now call biology. Although Renaissance writers emphasised problems of cognition, emotion and volition (the main subjects of De anima), the field also included a good deal of plant and animal physiology, based not only on the Parva naturalia but also on the ‘animal books' of Aristotle and to a lesser extent on the pseudo-Aristotelian De plantis.