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(4) Whether the soul is man, or is man composed of soul and body?
(5) Whether the soul is composed of matter and form?
(6) Whether the soul is incorruptible?
(7) Whether the soul is of the same species as an angel?
FIRST ARTICLE [I, Q. 75, Art. 1]
Whether the Soul Is a Body?
Objection 1: It would seem that the soul is a body. For the soul is the moving principle of the body. Nor does it move unless moved. First, because seemingly nothing can move unless it is itself moved, since nothing gives what it has not; for instance, what is not hot does not give heat. Secondly, because if there be anything that moves and is not moved, it must be the cause of eternal, unchanging movement, as we find proved Phys. viii, 6; and this does not appear to be the case in the movement of an animal, which is caused by the soul. Therefore the soul is a mover moved. But every mover moved is a body. Therefore the soul is a body.
Obj. 2: Further, all knowledge is caused by means of a likeness. But there can be no likeness of a body to an incorporeal thing. If, therefore, the soul were not a body, it could not have knowledge of corporeal things.
Obj. 3: Further, between the mover and the moved there must be contact. But contact is only between bodies. Since, therefore, the soul moves the body, it seems that the soul must be a body.
_On the contrary,_ Augustine says (De Trin. vi, 6) that the soul "is simple in comparison with the body, inasmuch as it does not occupy space by its bulk."
_I answer that,_ To seek the nature of the soul, we must premise that the soul is defined as the first principle of life of those things which live: for we call living things "animate," [*i.e. having a soul] and those things which have no life, "inanimate." Now life is shown principally by