1. The Argument from Efficiency

40 Now efficiency can be considered either as a metaphysical or as a physical property. The metaphysical property is more extensive than the physical for "to give existence to another" is of broader scope than "to give existence by way of movement or change." And even if all existence were given in the latter fashion, the notion of the one is still not that of the other.

It is not efficiency as a physical attribute, however, but efficiency as the metaphysician considers it that provides a more effective way of proving God's existence, for there are more attributes in metaphysics than in physics whereby the existence of God can be established. It can be shown, for example, from "composition and simplicity," from "act and potency," from "one and many," from those features which are properties of being. Wherefore, if you find one extreme of the disjunction imperfectly realized in a creature, you conclude that the alternate, the perfect extreme exists in God.

Averroes, therefore, in attacking Avicenna at the end of Bk. I of the Physics is incorrect when he claims that to prove that God exists is the job of the physicist alone, because this can be established only by way of motion, and in no other way -- as if metaphysics began with a conclusion which was not evident in itself, but needed to be proved in physics (For Averroes asserts this falsehood at the end of the first book of the Physics). In point of fact, however, [God's existence] can be shown more truly and in a greater variety of ways by means of those metaphysical attributes which characterize being. The proof lies in this that the first efficient cause imparts not merely this fluid existence [called motion] but existence in an unqualified sense, which is still more perfect and widespread. Now the existence of a primacy in the higher class does not follow logically from the existence of a primary in a lower [or more specific] class, unless that member is the most noble. For example, this does not follow: "The most noble donkey exists, therefore the most noble animal exists." Consequently, from the property of being the most noble being, one can argue better to a primacy among beings than from the primacy characteristic of a prime mover.

41 Hence, we omit the physical argument by which a prime mover is shown to exist and, using the efficiency characteristic of beings, we argue that among beings there is one which is a first efficient cause. And this is Richard's argument in Bk. I, chapter eight On the Trinity.

Some being is not eternal, and therefore it does not exist of itself, neither is it caused by nothing, because nothing produces itself. Hence, it is from some other being. The latter either gives existence in virtue of something other than itself or not. And its existence, too, it either gets from another or not. If neither be true -- i.e., if it neither imparts existence in virtue of another nor receives its own existence from another -- then this is the first efficient cause, for such is the meaning of the term. But if either of the above alternatives holds [viz. if it receives existence, or imparts it to others only in virtue of another], then I inquire about the latter as I did before. One cannot go on this way ad infinitum. Hence, we end up with some first efficient cause, which neither imparts existence in virtue of another nor receives its own existence from another.

42 Objections, however, are raised against this argument. To begin with, it seems to beg the question, for it assumes that there is an order and a first among causes. But if no efficient cause is first, then both the order and the terminus in such causes would have to be denied.

43 Furthermore, inasmuch as the argument begins with a contingent premise, it does not seem to be a demonstration. For a demonstration proceeds from necessary premises, and everything exists contingently which owes its existence to God. Consequently, with reference to God this statement is contingent: "Some being is non-eternal," because from it this statement follows: "Some non-eternal being exists," and this latter is contingent.

44 Furthermore, since there is no demonstration of the reasoned fact, neither does there seem to be any demonstration of the simple fact. For, whenever some conclusion is established by a demonstration of the latter type, one can always set up a converse demonstration of the reasoned fact (from cause to effect). But from the existence of the first cause, the existence of other things cannot be inferred by a demonstration of the reasoned fact; therefore, neither is the converse relation demonstrable as a simple fact.

45 To solve these objections, then, know this to begin with. Incidental [per accidens] causes are not the same as causes that are ordered to one another incidentally, just as essential [per se] causes are not the same as causes essentially ordered to one another. For when I speak of essential [i.e. per se] and incidental [i.e. per accidens] causes, I express a one to one relationship, viz. between a cause and its effect. But when causes are said to be incidentally or essentially ordered, two causes are being considered with reference to a single effect, so that we have a two to one relationship. Now causes are essentially ordered if one is ordered to the other so that [together] they cause a third thing, the effect. But causes are incidentally ordered if one is not ordered to the other in the very act of causing the effect. This would be the case with father and grandfather with regard to the son.

46 Secondly, it follows from this that essentially ordered causes differ from incidentally ordered causes in a threefold way:

The first difference is this: one cause depends essentially upon the other in order to produce an effect, which is not the case with causes that are ordered to a single effect only incidentally. Wherefore, the single causality of one of the incidentally ordered causes suffices to produce the single effect, whereas the causality of only one of the essentially ordered causes does not suffice.

47 From this, the second difference follows, viz. where essentially ordered causes are concerned, their causality differs in kind and they are not related to their effect in the same way. But the causality of all the incidentally ordered causes is of the same kind, since they can be referred immediately to the same effect.

48 From this, too, the third difference arises, viz. that the causalities of all of the essentially ordered causes concur simultaneously to produce the effect. For what is needed to cause an effect is that all its necessary causes concur. But all the essentially ordered causes are necessary causes. Therefore, all such must actually concur to bring about the effect. But this is not required where incidentally ordered causes are concerned, because each of itself possesses perfect causality as regards its effect, and they are of one kind so far as their immediate effect is concerned.

49 With these things presupposed, then, what remains to be shown is that the proof for a first cause does not involve a begging of the question. Therefore, I first prove that there is such a first where essentially ordered causes are concerned. I do this:

First, by the argument of the Philosopher, Bk. II of the Metaphysics (and that of Avicenna, too, Bk. VIII, chapter one) which seems to be this: All causes intermediate between the first and the last, cause by virtue of the first, so that their causality is derived from the first. As the Philosopher points out there, it is not derived from the last but from the first, for if "to cause" pertains to any of them, a fortiori it will pertain to the first. Now the minor of his argument seems to be this: "If the series of causes is infinite then all are intermediate causes." Consequently they all cause in virtue of some first cause, so that it is necessary to assume a first among efficient causes.

50 But you may object: When you say in the minor, "Every cause in an infinite series is an intermediate cause," either you mean by intermediate such causes as lie between a first and a last in the series, and so assume that there is a first, or else you mean it in a purely negative sense [i.e. as being neither the first nor last], in which case there are four terms, and again the conclusion does not follow.

51 I say, therefore, that the statement first assumed by the Philosopher is not the major in the argument, but is antecedent thereto. The argument, consequently, goes in this way. Every intermediary cause having a first and a last, derives its causality from the first. Hence the causality of the intermediary causes comes from the first. But if there were an infinity of such causes, they would all be intermediary. Hence, their causality is derived from some first. But if they are infinite, then there is no first. Hence, there is and there is not a first cause!

Proof of the aforesaid consequence:

All causes in anyway intermediate, be they positively or negatively so, are caused. Therefore, the whole concatenation of intermediary causes is caused. Hence, it is caused by something which is outside the concatenated series. Hence, there is a first.

52 What is more, the causalities of all the essential causes must concur simultaneously to produce their effect, as was pointed out above. But an infinity of things cannot so concur to produce one thing, hence there is not an infinity of such causes and therefore a first cause does exist.

53 Furthermore, a cause which is prior as regards the causation has a more perfect causality, and the more it is prior, the more perfect its causality. Hence, a cause with infinite priority would have an infinite causality. But if there were an infinite regress in essentially ordered causes, then there is a cause with infinite priority. To assume an infinite regress, then, is to grant a cause whose causality is infinite. But surely a cause which exercises infinite causality when it causes, does not depend upon anything else, and as such it would be the first. Therefore, etc.

54 Furthermore, to be able to produce something is not a property which of itself entails imperfection. But whatever is of such like is able to exist in something without imperfection. And thus there must be an efficient cause in which it can exist in this way, which is impossible if the cause does not produce its effect independently, and this means it is the first efficient cause. Therefore, etc.

55 Likewise, if one assumes an infinity of incidentally ordered causes, it still follows that there is a first in essentially ordered causes, for those causes which are incidentally ordered are in individuals of the same species. Then [one argues] as follows: No deformity is perpetual, unless it is brought about by a perpetual cause -- outside this coordination -- which perpetuates this deformity. Proof: Nothing that is part of this concatenation can be the cause of the whole of this perpetuated deformity, because in such incidentally ordered [causes], one is the cause of one only. Therefore, it is necessary to postulate -- beyond this deformed concatenation -- some first essential cause which perpetuates it. The deformation, then, is due to the deformed cause, but the continual uniformity of this deformity will be due to a cause outside this concatenation. And thus, if there is a process in incidentally ordered causes, there will still be a terminal point in some first essential cause upon which all the incidentally ordered causes depend.

In this way we avoid begging the question as regards a terminus and order of essential causes.

56 Now for the second objection raised against the aforesaid argument, viz. that it proceeds from something contingent, scil. "Something other than God exists." The philosophers would say that this is something necessary because of the essential order that holds between the cause and what it produces.

But I say, first, that even though it be contingent with reference to God, it is nevertheless most evident, so that anyone who would deny the existence of some being which is not eternal needs senses and punishment. And therefore, from what is contingent in this way we can establish something necessary, for from the contingent something necessary follows, but not vice versa.

57 Also, I say that although things other than God are actually contingent as regards their actual existence, this is not true with regard to potential existence. Wherefore, those things which are said to be contingent with reference to actual existence are necessary with respect to potential existence. Thus, though "Man exists" is contingent, "It is possible for man to exist" is necessary, because it does not include a contradiction as regards existence. For, for something other than God to be possible, then, is necessary. Being is divided into what must exist and what can but need not be. And just as necessity is of the very essence or constitution of what must be, so possibility is of the very essence of what can but need not be. Therefore, let the former argument be couched in terms of possible being and the propositions will become necessary. Thus: It is possible that something other than God exist which neither exists of itself (for then it would not be possible being) nor exists by reason of nothing. Therefore, it can exist by reason of another. Either this other can both exist and act in virtue of itself and not in virtue of another, or it cannot do so. If it can, then it can be the first cause, and if it can exist, it does exist -- as was proved above. If it cannot [both be and act independently of every other thing] and there is no infinite regress, then at some point we end up [with a first cause].

58 To the other objection (viz. that whenever an argument proceeds by way of a demonstration of simple fact, a converse demonstration of the reasoned fact can be constructed), one must say that such is not always true, because when we argue from the effect to the existence of a cause our argument may merely prove that the latter is a necessary condition rather than a sufficient reason for the effect. But it is only when the argument from effect to cause establishes the latter as a sufficient reason that the above principle [of converse demonstration] holds good.

59 And so we show from efficiency, to begin with, that something which is first exists, for -- as we have made clear -- something exists which makes all possible things possible. But that which makes all possibles possible cannot fail to exist of itself, for otherwise it would be from nothing. Therefore, it must needs be actually self-existent. And so our thesis is proved.