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appropriate object. Therefore the appetitive power should not be made a special genus of the powers of the soul.
Obj. 4: Further, the moving principle in animals is sense, intellect or appetite, as the Philosopher says (De Anima iii, 10). Therefore the motive power should not be added to the above as a special genus of soul.
_On the contrary,_ The Philosopher says (De Anima ii, 3), "The powers are the vegetative, the sensitive, the appetitive, the locomotion, and the intellectual."
_I answer that,_ There are five genera of powers of the soul, as above numbered. Of these, three are called souls, and four are called modes of living. The reason of this diversity lies in the various souls being distinguished accordingly as the operation of the soul transcends the operation of the corporeal nature in various ways; for the whole corporeal nature is subject to the soul, and is related to it as its matter and instrument. There exists, therefore, an operation of the soul which so far exceeds the corporeal nature that it is not even performed by any corporeal organ; and such is the operation of the _rational soul._ Below this, there is another operation of the soul, which is indeed performed through a corporeal organ, but not through a corporeal quality, and this is the operation of the _sensitive soul;_ for though hot and cold, wet and dry, and other such corporeal qualities are required for the work of the senses, yet they are not required in such a way that the operation of the senses takes place by virtue of such qualities; but only for the proper disposition of the organ. The lowest of the operations of the soul is that which is performed by a corporeal organ, and by virtue of a corporeal quality. Yet this transcends the operation of the corporeal nature; because the movements of bodies are caused by an extrinsic principle, while these operations are from an intrinsic principle; for this is common