Last time, we got some objections to the “unicity of the soul”; now we get the answers to those objections. Thomas says,
To set aside such quibbles, we should reflect that, in material things, one species surpasses another in perfection, in the way that, in numbers, species are diversified by adding one to another. Whatever perfection is found in lifeless bodies, plants also possess, and more besides. Again, whatever plants have, animals have too, and something else in addition. And thus we proceed until we come to man, the most perfect of bodily creatures. All that is imperfect is related as matter to what is more perfect. This is clear in the various classes of beings.
A plant is body that has life. It’s not like you can divide a plant into two pieces, one that’s the body and one that’s the life, like dividing a car into an engine and everything else. As you move down through the genera, each kind of body gets richer and richer, not composed of more and more parts.
The elements constitute the matter of bodies that are composed of similar parts; and again, bodies having similar parts are matter with respect to animals. And this is likewise to be observed in one and the same being. Among natural things, that which is endowed with a higher degree of perfection has, in virtue of its form, whatever perfection is found in lower nature, and in virtue of the same form has, besides, its own added perfection.
I think this is what I just said, though not so nicely.
Through its soul, the plant is a substance, and is corporeal, and besides is an animated body. Through its soul, an animal has all these perfections, and moreover is sentient. In addition to all this, man is intelligent through his soul. Thus, in any object, if we consider what pertains to the perfection of a lower grade of being, this will be material when compared with what pertains to the perfection of a higher grade. For example, if we observe that an animal has the life of a plant, this life is in some fashion material with respect to what pertains to sensitive life, which is characteristic of an animal.
“Material” and “formal” are two words that I boggle at once in a while. I understand what they mean in certain contexts, and then Thomas goes and uses them in some way that I don’t get. I assume that they have a wider meaning than I really get. Let’s see if I can tease it out.
A species, such as “animal”, is, of course, a form—or, at least, includes one in its definition. And “animal” represents something added to “plant”, as a form is added to matter and makes it something new, or gives it a new quality.
Genus, of course, is not matter, for then it would not be predicated of the whole. But it is something derived from matter; for the designation attaching to a thing in terms of what is material in it, is its genus.
I remember this from De Ente et Essentia (or perhaps it was Porphyry) but it made more sense then.
Specific difference is derived from the form of a thing in the same way. This is the reason why living or animated body is the genus of animal, and sensitive is the specific difference that constitutes it. Similarly, animal is the genus of man, and rational is the difference that constitutes him. Therefore, since the form of a higher grade of being comprises within itself all the perfections of a lower grade, there is not, in reality, one form from which genus is derived, and another from which specific difference is derived. Rather, genus is derived from a form so far as it has a perfection of lower degree, and specific difference is derived from the same form so far as it has a perfection of higher degree.
OK, now, this makes sense. No genus gives a thing form; no specific difference gives a thing form; only a species with actual individuals gives anything form.
Thus, although animal is the genus of man and rational is the specific difference constituting him, there need not be in man a sensitive soul distinct from the intellectual soul, as was urged in the first argument.
The first argument argued that an animal, having a sensitive soul, was in potency with respect to a rational soul, that is, that a rational soul is something that could be added. But “rational” is a specific difference, not a form; it can’t be added like that.
This indicates the solution of the second difficulty.
Which was that the intellect has no bodily organ whereas the sense does; thus, the intellect is separated from the body and the sense is not, and one thing can’t be both separated and unseparated.
As we have pointed out, the form of a higher species comprises within itself all the perfections of lower classes of being. We must note, however, that the species of a material being is higher in proportion as it is less subject to matter. And so the nobler a form is, the more it must be elevated above matter.
Hence the human soul, which is the noblest of all forms of matter, attains to the highest level of elevation, where it enjoys an activity that is independent of the concurrence of corporeal matter. Yet, since the same soul includes the perfection of lower levels, it also has activities in which corporeal matter shares. However, an activity is exercised by a thing in accordance with the thing’s power. Therefore the human soul must have some powers or potentialities that are principles of activities exercised through the body, and these must be actions of certain parts of the body. Such are the powers of the vegetative and sensitive parts. The soul has also certain powers that are the principles of activities exercised without the body. Such are the powers of the intellectual part, whose actions are not performed by any organs. For this reason both the possible intellect and the agent intellect are said to be separate; they have no organs as principles of their actions, such as sight and hearing have, but inhere in the soul alone, which is the form of the body. Hence we need not conclude, from the fact that the intellect is said to be separate and lacks a bodily organ, whereas neither of these is true of the senses, that the intellectual soul is distinct from the sensitive soul in man.
The intellect is separate from the body, but the soul as a whole is not. In animals, you might say that the soul is coextensive with the body, and contains in; in humans, it’s as though the soul extends a little bit beyond the body.
This also makes it clear that we are not forced to admit an intellectual soul distinct from the sensitive soul in man on the ground that the sensitive soul is corruptible whereas the intellectual soul is incorruptible, as the third objection set out to prove. Incorruptibility pertains to the intellectual part so far as it is separate. Therefore, as powers that are separate, in the sense mentioned above, and powers that are not separate, are all rooted in the same essence of the soul, there is nothing to prevent some of the powers of the soul from lapsing when the body perishes, while others remain incorruptible.
You can’t sense without senses…but it isn’t that the soul of a dead person lacks the power of sense, it just lacks the ability to make use of it. This is what makes the doctrine of the Resurrection of the Body so exciting; we’ll have new bodies, better than before, and all of our faculties will work better than ever.
The points already made lead to a solution of the fourth objection.
Which was that a human fetus is first a living body but not sentient, and then sentient but not rational, and then rational, and so these faculties are added as accidents to a base substance.
All natural movement gradually advances from imperfect to perfect. The same quality is receptive of greater and less; hence alteration, which is movement in quality, being unified and continuous in its progress from potency to act, advances from imperfect to perfect. But substantial form is not receptive of greater and less, for the substantial nature of each being exists indivisibly. Therefore natural generation does not proceed continuously through many intermediate stages from imperfect to perfect, but at each level of perfection a new generation and corruption must take place. Thus in the generation of a man the fetus first lives the life of a plant through the vecetative soul; next, when this form is removed by corruption it acquires, by a sort of new generation, a sensitive soul and lives the life of an animal; finally, when this soul is in turn removed by corruption, the ultimate and complete form is introduced. This is the rational soul, which comprises within itself whatever perfection was found in the previous forms.
With all due respect, I think Thomas must be wrong, here. He would have a human develop in stages, losing one soul then gaining another twice in the womb. It seems to me more likely that a human embryo gains a rational soul immediately, and then grows into it. The intellect requires sense phantasms to work upon, and it can’t get them until the body’s senses develop; but just as the soul of a dead man cannot exercise its sense, so the soul of an embryo cannot.