Part I (Prima Pars) Part 119 (1/2)

Objection 1: It would seem that the parts of the vegetative soul are not fittingly described--namely, the nutritive, augmentative, and generative. For these are called ”natural” forces. But the powers of the soul are above the natural forces. Therefore we should not cla.s.s the above forces as powers of the soul.

Obj. 2: Further, we should not a.s.sign a particular power of the soul to that which is common to living and non-living things. But generation is common to all things that can be generated and corrupted, whether living or not living. Therefore the generative force should not be cla.s.sed as a power of the soul.

Obj. 3: Further, the soul is more powerful than the body. But the body by the same force gives species and quant.i.ty; much more, therefore, does the soul. Therefore the augmentative power of the soul is not distinct from the generative power.

Obj. 4: Further, everything is preserved in being by that whereby it exists. But the generative power is that whereby a living thing exists. Therefore by the same power the living thing is preserved.

Now the nutritive force is directed to the preservation of the living thing (De Anima ii, 4), being ”a power which is capable of preserving whatever receives it.” Therefore we should not distinguish the nutritive power from the generative.

_On the contrary,_ The Philosopher says (De Anima ii, 2,4) that the operations of this soul are ”generation, the use of food,” and (cf.

_De Anima_ iii, 9) ”growth.”

_I answer that,_ The vegetative part has three powers. For the vegetative part, as we have said (A. 1), has for its object the body itself, living by the soul; for which body a triple operation of the soul is required. One is whereby it acquires existence, and to this is directed the _generative_ power. Another is whereby the living body acquires its due quant.i.ty; to this is directed the _augmentative_ power. Another is whereby the body of a living thing is preserved in its existence and in its due quant.i.ty; to this is directed the _nutritive_ power.

We must, however, observe a difference among these powers. The nutritive and the augmentative have their effect where they exist, since the body itself united to the soul grows and is preserved by the augmentative and nutritive powers which exist in one and the same soul. But the generative power has its effect, not in one and the same body but in another; for a thing cannot generate itself. Therefore the generative power, in a way, approaches to the dignity of the sensitive soul, which has an operation extending to extrinsic things, although in a more excellent and more universal manner; for that which is highest in an inferior nature approaches to that which is lowest in the higher nature, as is made clear by Dionysius (Div. Nom. vii).

Therefore, of these three powers, the generative has the greater finality, n.o.bility, and perfection, as the Philosopher says (De Anima ii, 4), for it belongs to a thing which is already perfect to ”produce another like unto itself.” And the generative power is served by the augmentative and nutritive powers; and the augmentative power by the nutritive.

Reply Obj. 1: Such forces are called natural, both because they produce an effect like that of nature, which also gives existence, quant.i.ty and preservation (although the above forces accomplish these things in a more perfect way); and because those forces perform their actions instrumentally, through the active and pa.s.sive qualities, which are the principles of natural actions.

Reply Obj. 2: Generation of inanimate things is entirely from an extrinsic source; whereas the generation of living things is in a higher way, through something in the living thing itself, which is the s.e.m.e.n containing the principle productive of the body. Therefore there must be in the living thing a power that prepares this s.e.m.e.n; and this is the generative power.

Reply Obj. 3: Since the generation of living things is from a s.e.m.e.n, it is necessary that in the beginning an animal of small size be generated. For this reason it must have a power in the soul, whereby it is brought to its appropriate size. But the inanimate body is generated from determinate matter by an extrinsic agent; therefore it receives at once its nature and its quant.i.ty, according to the condition of the matter.

Reply Obj. 4: As we have said above (A. 1), the operation of the vegetative principle is performed by means of heat, the property of which is to consume humidity. Therefore, in order to restore the humidity thus lost, the nutritive power is required, whereby the food is changed into the substance of the body. This is also necessary for the action of the augmentative and generative powers.

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THIRD ARTICLE [I, Q. 78, Art. 3]

Whether the Five Exterior Senses Are Properly Distinguished?

Objection 1: It would seem inaccurate to distinguish five exterior senses. For sense can know accidents. But there are many kinds of accidents. Therefore, as powers are distinguished by their objects, it seems that the senses are multiplied according to the number of the kinds of accidents.

Obj. 2: Further, magnitude and shape, and other things which are called ”common sensibles,” are ”not sensibles by accident,” but are contradistinguished from them by the Philosopher (De Anima ii, 6).

Now the diversity of objects, as such, diversifies the powers. Since, therefore, magnitude and shape are further from color than sound is, it seems that there is much more need for another sensitive power than can grasp magnitude or shape than for that which grasps color or sound.

Obj. 3: Further, one sense regards one contrariety; as sight regards white and black. But the sense of touch grasps several contraries; such as hot or cold, damp or dry, and suchlike. Therefore it is not a single sense but several. Therefore there are more than five senses.

Obj. 4: Further, a species is not divided against its genus. But taste is a kind of touch. Therefore it should not be cla.s.sed as a distinct sense of touch.

_On the contrary,_ The Philosopher says (De Anima iii, 1): ”There is no other besides the five senses.”

_I answer that,_ The reason of the distinction and number of the senses has been a.s.signed by some to the organs in which one or other of the elements preponderate, as water, air, or the like. By others it has been a.s.signed to the medium, which is either in conjunction or extrinsic and is either water or air, or such like. Others have ascribed it to the various natures of the sensible qualities, according as such quality belongs to a simple body or results from complexity. But none of these explanations is apt. For the powers are not for the organs, but the organs for the powers; wherefore there are not various powers for the reason that there are various organs; on the contrary, for this has nature provided a variety of organs, that they might be adapted to various powers. In the same way nature provided various mediums for the various senses, according to the convenience of the acts of the powers. And to be cognizant of the natures of sensible qualities does not pertain to the senses, but to the intellect.

The reason of the number and distinction of the exterior senses must therefore be ascribed to that which belongs to the senses properly and _per se._ Now, sense is a pa.s.sive power, and is naturally immuted by the exterior sensible. Wherefore the exterior cause of such immutation is what is _per se_ perceived by the sense, and according to the diversity of that exterior cause are the sensitive powers diversified.

Now, immutation is of two kinds, one natural, the other spiritual.

Natural immutation takes place by the form of the immuter being received according to its natural existence, into the thing immuted, as heat is received into the thing heated. Whereas spiritual immutation takes place by the form of the immuter being received, according to a spiritual mode of existence, into the thing immuted, as the form of color is received into the pupil which does not thereby become colored. Now, for the operation of the senses, a spiritual immutation is required, whereby an intention of the sensible form is effected in the sensile organ. Otherwise, if a natural immutation alone sufficed for the sense's action, all natural bodies would feel when they undergo alteration.

But in some senses we find spiritual immutation only, as in _sight:_ while in others we find not only spiritual but also a natural immutation; either on the part of the object only, or likewise on the part of the organ. On the part of the object we find natural immutation, as to place, in sound which is the object of _hearing;_ for sound is caused by percussion and commotion of air: and we find natural immutation by alteration, in odor which is the object of _smelling;_ for in order to exhale an odor, a body must be in a measure affected by heat. On the part of an organ, natural immutation takes place in _touch_ and _taste;_ for the hand that touches something hot becomes hot, while the tongue is moistened by the humidity of the flavored morsel. But the organs of smelling and hearing are not affected in their respective operations by any natural immutation unless indirectly.

Now, the sight, which is without natural immutation either in its organ or in its object, is the most spiritual, the most perfect, and the most universal of all the senses. After this comes the hearing and then the smell, which require a natural immutation on the part of the object; while local motion is more perfect than, and naturally prior to, the motion of alteration, as the Philosopher proves (Phys. viii, 7). Touch and taste are the most material of all: of the distinction of which we shall speak later on (ad 3, 4). Hence it is that the three other senses are not exercised through a medium united to them, to obviate any natural immutation in their organ; as happens as regards these two senses.