Chapter 4 — Coincidence of causes

Now that we have seen that there are four genera of causes, we must understand that it is not impossible that the same thing have many causes. For example, the statue whose causes are both the bronze and the artist: the artist is the efficient cause while the bronze is the material cause. Nor is it impossible that the same thing be the cause of contraries; for example, the captain is the cause of the safety of the ship and of its sinking. He is the cause of the latter by his absence and of the former by his presence.

Also, notice that it is possible that the same thing be a cause and the thing caused with respect to the same thing, but in diverse ways. For example, walking is sometimes the cause of health, as the efficient cause, but health is the cause of the walking, as the end: walking is sometimes on account of health. Also, the body is the matter of the soul, but the soul is the form of the body. The efficient cause is called a cause with respect to the end, since the end is actual only by the operation of the agent. But the end is called the cause of the efficient cause, since the efficient cause does not operate except by the intention of the end. Hence the efficient cause is the cause of that which is the end—for example, walking in order to be healthy. However, the efficient cause does not cause the end to be the end. Therefore, it is not the cause of the causality of the end; that is, it does not cause the end to be the final cause. For example, the doctor causes health to actually exist, but he does not cause health to be the end.

Also, the end is not the cause of that which is the efficient cause, but it is the cause of the efficient cause being an efficient cause. For example, health does not cause the doctor to be a doctor—I am speaking of the health which comes about by the doctor’s activity—but it causes the doctor to be an efficient cause. Therefore, the end is the cause of the causality of the efficient cause, because it causes the efficient cause to be an efficient cause. Likewise, the end causes the matter to be the matter and the form to be the form, since matter receives the form only for the sake of the end and the form perfects the matter only through the end. Therefore, we say that the end is the cause of causes, because it is the cause of the causality in all causes.

Also, we say that matter is the cause of the form, insofar as the form exists only in matter. Likewise, the form is the cause of the matter, insofar as matter has existence in act only through the form, because matter and form are spoken of in relation to each other, as is said in the second book of the Physics. They are also spoken of in relation to the composite, as the part to the whole and as the simple to the composed.

But, because every cause, as cause, is naturally prior to that which it causes, notice that we say a thing is prior in two ways, as Aristotle says in the History of Animals XVI. Because of this diversity, we can call something prior and posterior with respect to the same thing, both the cause and the thing caused. We say that one thing is prior to another from the point of view of generation and time, and likewise from the point of view of substance and completeness. Since the operation of nature proceeds from the imperfect to the perfect and from the incomplete to the complete, the imperfect is prior to the perfect (namely, from the point of view of generation and time), but the perfect prior to the imperfect from the point of view of substance. For example, we can say that the man is before the boy according to substance and completeness, but the boy is before the man according to generation and time.

But, although in generable things the imperfect is prior to the perfect and potency to act, when we consider that in one and the same thing the imperfect is prior to the perfect and potency to act, still, simply speaking, the act and the perfect must be prior, because it is what is in act that reduces potency to act and it is the perfect that perfects the imperfect. Matter is prior to form from the point of view of generation and time because that to which something comes is prior to that which comes to it. But form is prior to matter from the point of view of substance and completeness, because matter has completed existence only through the form. Likewise, the efficient cause is prior to the end from the point of view of generation and time, since the motion to the end comes from the efficient cause. But the end is prior to the efficient cause, insofar as it is the efficient cause from the point of view of substance and completeness, since the action of the efficient cause is completed only through the end. Therefore, these two causes, the material and the efficient, are prior by way of generation, but the form and the end are prior by way of perfection.

It must be noted that there are two kinds of necessity: absolute and conditional. Absolute necessity is that which proceeds from the causes prior by way of generation: the material and the efficient causes. An example of this is the necessity of death which comes from the matter: namely, the disposition of the composing contraries. This is called ‘absolute’ because it does not have an impediment. It is also called the necessity of matter. Conditional necessity, on the other hand, proceeds from causes posterior in generation: namely, the form and the end. For example, we say that conception is necessary if a man is to be generated. This is called ‘conditional’ because it is not necessary simply that this woman conceive, but only conditionally, namely, if a man is to be generated. This is called the necessity of the end.

Notice, also, that three causes can coincide in one thing—namely, the form, the end and the efficient cause—as is plain in the generation of fire. Fire generates fire; therefore, fire is the efficient cause insofar as it generates. Fire is also the formal cause insofar as it causes to exist actually that which before was in potency. Again, it is the end insofar as the operations of the agent are terminated in it and insofar as it is intended by the agent.

But the end is twofold: the end of generation and the end of the thing generated, as is plain in the generation of a knife. The form of the knife is the end of generation; but cutting, which is the operation of the knife, is the end of the thing generated, namely, of the knife. Moreover, the end of generation sometimes is coincident with the two aforementioned causes: namely, when generation takes place from what is similar in species, as when man generates man and the olive, an olive. But this cannot be understood of the end of the thing generated.

Notice that the end coincides with the form in something which is numerically the same, because that which is the form of the thing generated and that which is the end of generation are the same numerically. But it does not coincide with the efficient cause in a thing numerically the same, but in a thing specifically the same, because it is impossible that the maker and the thing made be numerically the same, but they can be specifically the same. Thus, when man generates man, the man generating and the one generated are numerically diverse, but they are specifically the same.

However, matter does not coincide with the others. This is because matter, by the fact that it is being in potency, has the nature of something imperfect; but the other causes, since they are in act, have the nature of something perfect. However, the perfect and the imperfect do not coincide in the same thing.