Whether hands should belong to the human alone.
Next one inquires whether hands should belong to the human alone.
1. It seems not. For the hand is the organ of organs. Therefore, those things that require organs equally, equally require hands. But brute animals need organs as much as the human does, since if these were lacking they would suffer a lack as much as would the human. Therefore, they need hands just as the human does.
2. In addition, nature always does that which is best. But it is better for the human to have hands than to have front feet. Therefore, by the same reasoning, it will be better for brute animals. Therefore, hands should not belong to the human alone.
The Philosopher says the opposite.
One must reply that hands belong to the human alone because the hand is just like an organ of the intellect, with which a human being especially executes whatever he entertains in the intellect, because just as through the intellect a human has a capacity for all things intelligible, so too through the hand he has a capacity for all things capable of being performed. Just as the human has an almost infinite power through the intellect, since he cannot understand a given number of things without being able to understand still more, so too with the hand he cannot do a given number of things without being able to do still more, should a reason arise. And although all the members obey the intellect and reason, yet none do so as much as the hand. Thus, when someone attempts to express something that he understands intimately, he can hardly restrain his hands, since the hand so completely obeys the intellect that it naturally tends to manifest in an outward act what is conceived internally in the soul. Thus the hand should belong only to an animal that has intellect, and since the human alone has intellect, this is why, etc.
Furthermore, the hand bears witness to a refined sense of touch, so that among all the members the power of touch flourishes especially in the hand, and this is why it belongs only to that animal which has the best sense of touch, and the human is of this sort. Thus one must reply briefly to the question that the hand exists for the sake of the intellect and an excellent sense of touch, and this is why it belongs only to the human.
1. On to the arguments. To the first, one must respond that although all animals require organs, nevertheless none does just as the human does, because every animal has some kind of armament by nature: one has horns, another talons, or teeth, or feet for flight, but the human, on the other hand, is lacking in every type of armament. Thus if he had by nature every type of armament, his body would be terribly unbalanced. And this is why nature did not give the human some armament naturally, but gave him hands with which he can make for himself every type of armament, in accord with his intellect and reason.
2. To the second argument one must respond that not everything that is better for one is better for another. It is good for sight that the eye have the disposition it has (namely, clear); nevertheless, it would not be good for the whole body to be just like the eye. Thus it is better for brute beasts to have feet rather than hands, because if they had hands they would only be able to use them as they use feet, owing to their lack of intellect and reason. And this is why, etc.
Whether a human should naturally have wings and fins.
Next one inquires whether a human naturally should have wings and fins or whether naturally he might swim or fly.
1. It seems so. For whatever is lighter can better be supported in something light. But a human is lighter than birds and fish. Therefore, he can be supported in the air better than a bird and in water better than a fish. The major [premise] is clear, and the minor [premise] declares that heat is the cause of lightness, and there is more heat in the human than in other animals.
2. In addition, a dead human floats in water. Therefore, much more so a live one, since a live one is lighter than a dead one, as is evident by experience [per experimentum] since a dead one is heavier than a live one for those carrying him, because four can hardly carry a dead man while two can carry a live one with ease.
The opposite is clear.
One must respond that it is not natural for a human to swim or to fly, because through his reason and through his hands the human has the power to form instruments for himself, by means of which he can pass through water just like a fish, and this is why he makes a ship and why he does not require the fins that fish have.
Furthermore, there are fewer fumes in the human than in birds. An indication of this is that, just as birds have feathers, so there are hairs on a human, and these hairs are small when compared to birds' feathers. Therefore, compared to birds, hairs do not have the power that feathers have for supporting a body in air. Because feathers are wide, they therefore are held up by air; hairs, however, are long and more earthy, and this is why they cut through the air and seek the ground, which is the [natural] place for heavy things. Thus a capacity for walking is a proper characteristic of the human, just as is the capacity for receiving instruction, and contrary differentiae do not suit him well. And the entire reason is that nature acts for an end, and fish seek their nutriment in water, and birds do so in air, but the human does this especially on the ground, and this is why nature better provided him with instruments for walking, like feet, rather than for swimming or flying. This is why, etc.
1. On to the arguments. One must respond to the first that one has more heat in two ways: either quantitativelyand thus a human has more heat than fish and birdsor proportionally in comparison to other qualities, and in this way birds have more heat. Thus their flesh is hot and dry, and this is why, even though these animals are not as hot as the human, nevertheless they have instruments by means of which they can be borne on the air and water. The human lacks these instruments, and this is why, etc.
2. To the second argument one must reply that a live human being is governed by a natural rule [regimen naturale], and because there is in his body more earth than other elements (because, according to the Philosopher, mixed bodies are dominated by earth and water), for that reason a live one seeks the bottom. But a container changes the content toward its disposition, and this is why, if the body of a dead human lies in the water for a long time, the water dissolves the earthy parts and converts them to its nature, and this is why such a dead body does not seek the bottom but rather floats.
And, besides this, every contrary naturally flees from its contrary, so far as possible. Now the dead body of a human is most unclean, and water is a clean element, and this is why water naturally struggles as far as it is able to expel a dead body using the power of contrariety, and this is also why it does not cease to act on that body until the body moves, so that the water may expel the body by this motion.
Some say that this is owing to the fact that a living human being seeks the bottom due to its weight, since, according to the Philosopher, he is dominated like other mixed bodies by earth and water. But in a dead one, bile [ fel] is separated from the gall bladder and distributed to the individual members, making them light, because it is of the nature of fire. This is why it floats, etc.
Others say that when a human dies and sinks to the bottom, and the water then enters in and fills the porous memberslike the stomach, bladder, lungs, and others of this sortand once the air is expelled, the water enters in, lest there occur a vacuum. As a result the body is lifted up, and it floats, etc.
Still others say that earlier the body had moisture in its own right. But when it is dead, the water surrounding it moves that little moisture toward itself, along with its body. And this is why it floats, etc.
Whether in respect to motive parts bloodless animals should surpass those with blood.
Next one inquires whether in respect to motive parts bloodless animals should surpass those with blood.
1. It seems not. Because the more noble a nature is, the more it requires many things. Therefore, animals with blood need more organs than bloodless ones.
2. Moreover, some bloodless animals, like serpents, fish, and many others, lack feet. Therefore, it is not reasonable that blooded animals should have fewer feet.
The Philosopher says the opposite.
One must respond that the more noble a nature is, the more power it has and the more it needs several instruments. And because blooded animals are better than bloodless ones, this is why they require several parts according to their species. But because those that are bloodless have hard and poor flesh and are exceedingly cold owing to their lack of blood, for this reason it is necessary that they simply be immobile or that they have several motive parts. And this is why the number of feet among animals that move does not exceed the number four, or the number two for wings, whereas animals without blood have to have several feet and several wings, because owing to the weakness of their nature they cannot move with fewer.
1. On to the arguments. To the first argument one must reply that the more noble a nature is, the more parts it demands according to its species, but nevertheless it does not require several parts with respect to number for its operation, because, owing to the perfection of its nature and the strength of its power, it can accomplish this with few with respect to number, whereas the more imperfect can only accomplish this with several.
2. To the second argument one must respond that the serpent and an animal of this type does not need feet owing to the hardness and viscosity of its flesh, and likewise on account of its flexibility. This is why it uses these in place of feet, etc.