Whether this power is corrupted once the fetus is formed.
Next one asks whether this power is corrupted once the fetus is formed.
1. And it seems not. In those having a right order, the power of that which is prior exists in that which is posterior. Therefore, the father's power is in the son that has been formed. But this would not be so if the power flowing from the father's soul were corrupt.
2. In addition, if this power were corrupted once the fetus has been formed, then it would be corrupted either from itself or from the fetus. But it is not from itself because nothing causes its own corruption, nor is it from the fetus, because it introduces form to the fetus, and an effect does not corrupt its cause.
3. The Philosopher says the same thing. For he says that it is inappropriate to say that this power is corrupted.
To the contrary. Every power exists in order to act. Therefore, something that does not exist in order to act is useless. But if this power exists once the fetus is formed, then it would not exist in order to act, and therefore, it would be useless. But nothing like this occurs in nature. Therefore, etc.
One must respond that the power derived from the father is two-fold. One is ordered toward the preparation of matter and the induction of form. Another power is consequent to the introduction of form, and this one is ordered toward operations similar to those of a principal agent. Once the fetus is completed, the first power departs and disappears into itself. This is similar to the motion of projectiles, because as long as a rock is in motion there always remains some power of the one impelling or projecting it, but when it approaches its ultimate end and comes to rest, then the power of the one first projecting it forward disappears. Thus the premise is correct. The power that has been separated from the father's soul along with the sperm resides in a sort of frothy, airy, mossy spirit, and so long as the fetus is being formed, this spirit and, as a result, this power always remain. But when the fetus has been completed, this spirit is resolved into various superfluities, and the power that was in it earlier disappears. The power that follows after the soul, however, remains in the fetus as long as the soul endures, and this power is still said to come from the father's soul because it depends on him as cause and effect. Thus, just as the soul of the one that has been generated is said to be from the father, so the power of this one is said to come from him too.
1. On to the arguments. To the first, one must respond that the father's power is in the fetus. But this is not the same as that one that earlier was ordered toward the soulthat is, which preceded the soulbut is rather the one that follows the soul.
2. To the second argument one must reply that this power is corrupted neither by itself nor by the fetus, but is rather corrupted by its containerthat is, by the one that is nearest to it because "the generation of one thing is always the corruption of another," according to the thought of the Philosopher. Thus the embryo's generation brings the semen's corruption.
3. To the third argument one must reply that the Philosopher says this by way of arguing that it is inappropriate for the form to be corrupted, because similarly he also says that it is inappropriate that it [the form] remain. In the same way a solution is apparent for the other.
Whether the soul's power operates through a mediating heat.
Next one asks whether it is necessary for heat to be in the semen or whether the soul's power operates through a mediating heat.
1. And it seems not. Because things mixed from earth and water coagulate in the cold, and cold dominates in ones like these. But all things that are generated from earth and water here below, in the sphere of active and passive [things], coagulate; therefore, they are generated by cold.
2. In addition, according to the Philosopher in the fourth book of the On Meteorology [De meteora], corruption is of two types. One is natural, and putrefaction is like this and occurs principally from heat and moisture, as he says in the same place. The other is unnatural, and this occurs by violence. Since, therefore, the power in the semen works toward life, and since heat is the principle of corruption, as touch is, it does not operate with a mediating heat.
3. In addition, nature aims at what is the better thing among those things that are possible. But although heat conserves a thing, nevertheless it also continuously consumes either the subject or the object, whereas cold preserves it for a longer period, as is evident in things congealed by cold, for example, in a crystal. Therefore, since the soul's power acts toward conservation, it acts more with a mediating cold than with heat.
The Philosopher says the opposite.
One must respond that this power acts in sperm with a heat mediating just like an instrument, because heat and cold are active principles, and the nobler a form is, the nobler the instrument by which it operates. Thus superior or celestial bodies act with a mediating light, which is a nobler thing among active bodies. But among these inferior things, soul is the noblest form. Therefore, it acts with a nobler mediating instrument. But heat is nobler than cold, just as a habitus is nobler than a privation. Therefore, etc.
Moreover, according to Aristotle in the book On the Reason for Shortness or Length of Life, heat is the principle of life, and its movement occurs from the center to the circumference. Contrariwise the movement of cold occurs from the circumference to the center and consequently it is the cause of mortification. Thus, the soul's power operates both with a mediating heat and cold, yet more often with a mediating heat since, according to Avicenna, the role of heat is common to the entire body and because, according to Hippocrates, heat is nature's friend, whereas cold is like food for heat since cold tempers heat, keeping the heat from fully performing its consuming action.
1. On to the arguments. To the first, one must respond that not all things coagulated from earth and water are coagulated by cold; to the contrary, they can be coagulated by heat. For if something is mixed from earth and water, heat can evaporate parts of the water, and after these are evaporated, that which remains draws together, hardens, and coagulates, as is clear in the case of mud once the water has been evaporated from it by the sun. And this is the case too in the production of the fetus, since the heat existing in it consumes the watery and superfluous moistures and evaporates them, and this is the reason why what remains is more solid and compact and is transformed into members. Thus heat causes it to come together by consuming that which is thin and by acting on the power of the soul. The soul operates from an end, and the heat acts in an instrumental fashion under the soul's power as an axe hews under the power of a craftsman, etc.
2. To the second argument one must reply that heat is of two types: natural and accidental. The cause of putrefaction is an extraneous and accidental heat, and this is why "the generation of one thing is the corruption of another." This is why one cannot be generated unless another is corrupted. Thus, since the power in the semen intends to produce a fetus, it must necessarily act with some mediating power that can corrupt the semen, and heat is something very much like this.
3. To the third argument one must reply that although cold things last longer in some things, as in a crystal and things like this, nevertheless in animated beings warmer things last longer, according to the Philosopher in the book On the Reason for Shortness or Length of Life.
-  A. contrasts here a habitusa quality, characteristic, or relationship that is possessed by an objectwith its privation or absence.