Which elements predominate in homogenous parts.
Further, one inquires which elements predominate in homogenous parts.
1. It seems that the light elements do. Now, life depends on heat and moisture. Therefore, those things that are warm and moist especially predominate in living things.
2. Moreover, when many things come together or toward some one other thing, and these things have greater power, they gain dominance. But light elements have greater power than heavy elements. Therefore, they predominate in a mixture.
To the contrary. Earth and water hold dominion in those things that are generated around a midpoint. But all living things are generated in this way, and therefore, etc.
One must respond that earth and water predominate in the homogenous parts of all living beings. And this is the reason: if several things come together, some will have greater power than others, so it is necessary that the weaker ones be increased in quantity in order to bring the whole thing into balance. For if one stronger in power were greater in quantity, it would immediately corrupt the other [weaker] one and convert it into its own nature. But heavy elements have less power for acting than do the light elements, and this is why it is reasonable that they are more abundant in quantity. An indication of this is that a mixed [body] is changed by the movement of the dominant element in it, and the movement of any mixed body whatsoever, is downward, to the extent that it is mixed. Therefore, the heavy elements predominate in it.
1. To the arguments. To the first, one should respond that heat is of two kinds: namely, elemental, and a certain tempered or proportionate one. Life is not supported by the first type, since this is repugnant to life, but rather life is supported by the second type. And such a heat can exist in a thing in which the heavy elements abound or predominate materially.
2. To the second argument one should respond that if light elements were either equal to or greater in quantity, they would attract or convert the others to their nature. But this is not the case, as has been said.
Whether official parts are composed from homogenous ones by means of continuity.
It is asked further whether official parts are composed from homogenous ones by means of continuity or of contiguity.
1. It seems not. An end is not composed from those things which exist for the end, because the end is an extrinsic cause. But homogenous parts exist on account of official parts, as is said in the text. Therefore, they do not compose them.
2. In addition, something is continuous whose motion is one and in which there is uniformity in the parts. But the motion of an official part is not always one nor always uniform in every part. Therefore, it is not composed from these by means of continuity. Nor is it by means of contiguity, because things are contiguous whose extremities exist simultaneously, but not as one. But this cannot be said of homogenous parts. For if this were the case, then they would not share in one form.
The Philosopher says the opposite.
One must reply that official parts are composed from homogenous parts. Now, official parts have various operations: consider that the tongue discerns tastes, and forms sounds [voces], and softens or grinds up nourishment, and so too for the others. Likewise, the hand receives and retains, extends and contracts. And this is why it is formed from various parts.
1. To the arguments. To the first, one should respond that an end is of two types: intrinsic and extrinsic. An intrinsic end is a thing's form and it is properly the end of generation, since once this form is achieved generation ceases. An extrinsic end belongs to the very thing generated. Moreover, an intrinsic end is of two types: near and remote. The near end, however, is the proper operation of a homogenous part, because each part exists for its own particular work. But the remote end is the official part. This is why in all things that are generated in an ordered way the first one generated exists for the sake of the last.
Or, on the contrary, one may say correctly that the official part is the intrinsic and near end of the homogenous parts, because the perfective form of the official part is the perfection of a homogenous part, just as the form of the whole is the perfection of each part. The proper operation is the more remote end, because it is a secondary act. The extrinsic end of these homogenous parts, however, is the human, since all these lower things exist on account of the human and the human exists on account of the first cause. Through this a response to the first argument is clear.
2. To the second, one must respond that something can be continuous in two ways: either in nature or in quantity, so that if a line is drawn out straight, half of which is white and half black, that surface can be continuous with respect to its quantity, although it will not be continuous or uniform in terms of color. It is the same for homogenous parts. They are continuous in terms of location and in quantity, but they are discontinuous or contiguous respecting their own natures.