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Man stands in the middle of the meeting point between living things and the things of heaven.
The soul is immaterial, but is acting with the body to complete the full function of that particular animal. Aquinas proves the soul exists but is not the body. The Soul is the first principle of life and Aquinas proves nothing corporeal can be a first principle of life so the soul, "is not a body, but the act of a body".[2] This life principle is important to understand and may be easy to understand as from a physical point of view. That which is moved has to be moved by a force, but where does this first force come from? "As everything which is in motion must be moved by something else, a process which cannot be prolonged indefinitely, we must allow that not every mover is moved."[3] The Body does not consist of matter alone. Matter cannot be the first principle or life source because, “since, if that were the case, every body would be a living thing, or a principle of life.”[4] We see that this is absurd and no rock or thing is living. Those bodies which are living, owes this life to some principle which is called its act.” [5]
The next task for Aquinas is to prove that the soul is subsistent. This has to do with whether the soul dies with the body or lives on after death. Aquinas says that the soul with its intellectual powers does not need the body for certain operations such as the ability to understand concepts or phantasms and therefore subsist after the death of the body. This is opposed to what is stated in article 4 where the souls of animals and plants do not subsist without the body because there souls are not rational. Aquinas then goes on to ask whether the soul is a man, or is a man composed of soul and body? This has to do with defining the soul more and more towards individual men. Do all men have souls or do we share a single soul? Aquinas says that each man has a soul and it corresponds to the individual flesh of this man. He concludes, “This soul is the man.”[6]
The soul is composed of matter and form, as a whole compound. We are a sympositum, which illustrates how essentially united the body is to the soul. The soul is the form of the whole body and gives it all of its function and powers. The soul as the form of man becomes the act of his body. The soul is not the potential or part of the act of the soul. Matter is the principle by which forms are made individuals so we can say this soul and this body. Form is related more to how a body moves and is the mover of the body. We see this composition of matter and form serving to describe the soul as it pertains to eternal life or damnation.
