Question:
Answer:
The soul is not in any particular part of the body, such as the brain. If it were, then other parts of the body would not be living matter, since all of the life-giving power of the soul would be only in that part in which it subsisted. The parts of the body that didn’t have the soul would be akin to a hand or leg that’s been cut off from the body. It would be simply a clump of non-living matter.
But obviously this is not the case. Every part of your body is living matter, unified into the one life that is yours. Therefore, the soul and all its life-giving power is present to every single part of your body. In other words, there is no part of your body that does not have the soul present to it.
This is why Aristotle and St. Thomas Aquinas called the soul the form of the body. It is that principle within living beings that makes the body the kind of body it is—namely, a living body. But more than that, for humans the soul is unique in that it makes the living body a human body, capable of activities that belong to the kind of animal that we are—namely, a rational animal.
For a great explanation of the soul, see Michael Augros, The Immortal in You: How Human Nature is More Than Science Can Say, published by Ignatius Press.