In Aristotle's thought, life and soul are universal phenomena extending from plants to human beings. The human being contains within himself powers shared with plants and powers shared with animals.

Aristotle conceives the human soul as having a structure composed of three basic levels:
At the first, or vegetative, level lies the most basic form of life, which secures human persistence and survival.
At the second level are desires and emotions, which are also found in animals.
At the third level is rationality, which is unique to the human being.

This division of the human psyche into three levels can, in a different form, also be seen today in evolutionary psychology, which describes the human brain as consisting of three levels: first, the archicortex, or the level of basic life; second, the paleocortex, or the animal level of the brain; and third, the neocortex, which encompasses rationality and self-awareness in the human being.

In Aristotelian thought, the human being is a rational creature who reaches fulfilment and flourishing only by making the fullest use of rationality. In Aristotle's view, the human being possesses within rationality everything required for this development. This differs from the Platonic view, which affirms a truth larger than and transcending human existence.

After Plato and Aristotle, these two ways of understanding the human soul continued through different philosophical traditions. One may say that philosophical perspectives have continued to shape different schools of psychology up to the present, just as we can see rebirths of Platonic and Aristotelian thought in different branches of analytical and psychological traditions and in the ways they understand the human psyche.

Video on the “Steps into Light” YouTube channel:
https://youtu.be/f6P-L2Huh7M