Whether the soul is in the sperm.
How we have already declared that the powers," etc. About this sixteenth book he asks first whether the soul is in the sperm.
1. It seems that it is. For everything that has any consequent operations has a principle of these operations. But semen has operations, of which the soul is the principle, because it is nourished and grows and is moved, and these things are found only in animated things. Therefore, etc.
2. In addition, nothing acts except through that which is already in act. But the soul's active power is in the semen, and generation is of like from like. Therefore, the soul is in the semen in an act for which it is the power.
3. In addition, an eye that does not have the form of the eye is an eye only equivocally. By the same reasoning, then, if the semen does not have soul (which is the principle of these operations and the source for these powers [ potentiae]the augmentative, nutritive, and generative), then it is semen equivocally because these are found in semen just as sight is in the eye.
4. In addition, "complete" and "incomplete" do not distinguish essence or species. But semen is related to the animal as something incomplete is to one complete. Therefore, these do not distinguish them in essence. But this would not be so if the semen did not have the soul; therefore, etc.
The Philosopher says the opposite, for he says that the soul is not in the semen in act but only in potency.
To this, one must say that the soul is not in the semen in act but in potency. Nevertheless, the power of the soul is in the semen in act, because just as the prime mover acts in the motion of projectiles by imparting some power to a second, moving thing, by which the second can move after the first ceases to do so, so too is a certain power separated from the father along with the sperm, and this power moves and operates after the father is at rest. Thus the power in the semen is the power of the soul which is derived from the soul of the father with the sperm, and which produces the soul in the semen itself, and yet is not the soul in act because "soul is the act of a physical, organic body," etc. And with respect to the vegetative [soul], it requires homogeneous parts, and with respect to the sensitive it requires official [parts]. But in the semen, since it is not an organic body, there are neither homogeneous parts (like flesh and bone and things of this sort) nor official ones (like the foot and things of this sort). Thus the soul is not in the semen itself in act. Thus the Philosopher says in the seventh book of the Metaphysics that "sperm acts just like those things which come from art." Because just as a house does not exist in the mind of the architect in act, neither is the soul in the semen in act, but only in potency. And in the second book of On the Soul the Philosopher says that the soul is the act of a body having life in potency, not in the sense that it casts off the soul as it does the semen, but rather implying that the soul is not in the semen in act.
1. On to the arguments. To the first, one must respond that the operations that are attributed to the sperm or the semen are from the power that is in the sperm. This power, however, is in spirit as if in a subject, yet it acts through the power of a separate agent, namely, the father's soul, from which it is derived.
2. To the second argument one must reply that semen acts through a power that is in semen in act, but it does not act through the soul.
3. To the third argument one must reply that something is called an eye equivocally if it does not have sight, and is not so called because it does not see in act (for example, the eye of one who is sleeping). So, contrariwise, semen is correctly called semen equivocally if it does not have power, but not if it does not have soul.
4. To the last argument one must reply that "complete" and "incomplete" do not distinguish an essence in the same form, in the way that something is more or less white. Nevertheless, if these are in different forms, they do distinguish the essence, just as they do for substance and accident which are related to one another as complete and incomplete. Thus the premise is correct. The forms of the semen and the animal are different and contraries, as it were; otherwise, the form of the semen would not be corrupted during the animal's generation. But they are said to relate to one another as complete and incomplete, because once the semen's form has been cast off from the matter of the semen, it exists in potency to the form of the animal, and the semen's matter is potentially that which the animal is in act. Nevertheless, this act cannot be introduced while the form of the semen remains, and this is why the argument does not succeed.