Aristotle was undoubtedly the most brilliant student of Plato. Yet, Aristotle diverged from most of Plato’s fundamental philosophies, especially on the concept of the self.
As we may already know, Plato is sure that the true self is the soul, not the body. And to be specific, the true self for Plato is the rational soul which is separable from the body. Aristotle’s concept of the self is quite the opposite.
Aristotle’s concept of the self is more complicated as he talked about so many things in this topic. However, there is one main theme in Aristotle’s narrative of the soul that guides us in understanding his concept of the self, that is, the human person is a “rational animal”. In other words, for Aristotle, the human person is simply an animal that thinks.
How did Aristotle come up with the idea that the human person is just an animal that thinks? His idea of the soul provides the key.
Aristotle defines the soul as the principle of life. And as the principle of life, it causes the body to live. This explains why for Aristotle all living beings have souls. Because for Aristotle all living beings have souls, then it follows that plants and animals (in addition to humans) have souls too. Thus, Aristotle distinguishes three levels of soul, namely, vegetative soul, sensitive soul, and rational soul.
According to Aristotle, the vegetative soul is found in plants, while the sensitive and rational souls are found in animals and humans respectively.
According to Aristotle, plants have souls because they possess the three basic requirements for something to be called a “living being”, that is, the capacity to grow, reproduce, and feed itself.
Sensitive souls also grow, reproduce, and feed themselves; but unlike vegetative souls, sensitive souls are capable of sensation.
Finally, rational souls grow, reproduce, feed themselves, and feel; but unlike the sensitive souls, rational souls are capable of thinking. According to Aristotle, this highest level of soul is present only in humans.
Since humans possess all the characteristics of animals, that is, the capacity to grow, reproduce, feed itself, and feel, in addition to being rational, Aristotle concludes that the human person is just an animal that thinks. As Aristotle’s famous dictum on the human person goes, “Man is a rational animal.”
Again, this explains why for Aristotle the human person is just an animal that thinks.
Now, for Aristotle, the human person is not a soul distinct from the body as Plato would have us believe. Aristotle argues that the self or the human person is a composite of body and soul and that the two are inseparable. Aristotle’s concept of the self, therefore, was constructed in terms of hylomorphism.
Aristotle views the soul as the “form” of the human body. And as “form” of the body, the soul is the very structure of the human body which allows humans to perform activities of life, such as thinking, willing, imagining, desiring, and perceiving.
While Aristotle believes that the human person is essentially body and soul, he was led to interpret the “true self” of humans as the soul that animates the body. However, Aristotle believes that the body is as important as the soul as it serves as “matter” to the soul.
Although Aristotle contends that the soul is the form of the body, he did not argue for the primacy of the former over the latter. Again, Aristotle’s concept of the self is hylomorphic, that is, the self or the human person is composed of body and soul. The two are inseparable. Thus, we cannot talk about the self with a soul only or a self with a body only. For Aristotle, the self is essentially body and soul. Indeed, for Aristotle, the self is a unified creature.