In the history of Western thought, two conceptions of the soul have competed for dominance, one associated with Plato and the other with Aristotle. For the Platonist, your soul is the real you, and your body merely a vehicle to which it is temporarily attached—indeed, your body is a kind of prison from which the soul needs to be liberated. For the Aristotelian, by contrast, our bodies are no less essential to us than our souls are. Only soul and body together make a complete person.
Descartes adopted something like Plato’s view, though his Catholicism prevented him from treating the body as a prison. He argued that the causal connection between soul and body is so intimate that it is misleading to think of the latter as a mere vehicle. Still, like Plato, he regarded soul and body as two distinct substances, each a complete entity in its own right and only contingently associated with the other. This Platonic-Cartesian position is known as substance dualism.