This article stresses the main lines of Thomas Aquinas’s philosophy on
the nature of the body-soul union. Following Aristotle, Aquinas sees the soul as
a ‘principle of life’ which is intimately bound to a body.
Together they form a non-contingent composition. In addition, the distinctive
feature of the human soul is rationality, which implies that a human needs a
mind to be what it is. However, this is not to say, as Descartes proposes, that
the reason that I am a human is that I am fully self-conscious. On the contrary,
I will show that self-consciousness is not necessarily a key to defining a human
being. To that aim, and based on Aquinas’s views, I draw a
distinction between what I will call ‘egos’ and ‘selves’.