Aristotle begins abruptly with a statement of the four typical causes.2 But before reviewing his discussion of them we ought to know the meaning of cause itself, and its bearing in Aristotelian philosophy generally. This knowledge we shall first provide.
1. The Aristotelian Notion of Cause
Neither in Aristotle nor in St. Thomas does one find a complete, systematic account on cause. The nearest thing to it in Aristotle is the chapter of the Physics in which he tells the kinds of causes and their modes.3 Yet the idea of cause is everywhere made use of in their writings, in logic, physics, metaphysics, theodicy, theology. Hence, by comparing the numerous passages in which they speak of cause, what they meant by this notion still becomes reasonably clear.
Broadly speaking, the Aristotelian notion of cause contains two essential notes. A cause is a principle of being, and secondly, in the order of knowledge, a principle of explanation. Primarily, it is a principle of being, of concrete reality. Everything that is, save God, depends on something not only for its being but also for its becoming. This something, of whatever sort, is a cause. "Those things are named causes," says St. Thomas, "on which other things depend for their existence or becoming":
causae autem dicuntur ex quibus res dependent secundum esse swum vel fieri.4
John of St. Thomas' definition strives for greater precision; it reads: causa est principium alicujus per modum influxus seu derivationis, ex qua natum est aliquid consequi secundum dependentiam in esse.5
A principle of being, cause is by that very fact a principle of understanding and explaining reality. It is, in fact, a necessary means of acquiring what Aristotle calls scientific knowledge; science, by his definition, is precisely knowledge through causes: scientia est cognitio per causas. On this fundamental rests his entire logic of demonstration, all his scientific methodology, down to the last iota. And when, in the chapters of the Physics we are now to consider, he introduces the notion of cause, this is the aspect put forward - cause as a principle of explanation.
2. The Four Causes
Aristotle's enumeration of causes is universally accepted in the Aristotelian and the Scholastic tradition. i) Material cause, 2) formal cause, 3) efficient cause, 4) final cause, these are the four causes.6 The division is, in fact, based on the essential types of causality that can be discovered in reality: diversas rationes causandi, as St. Thomas expresses it. The distinction of the four causes is therefore a distinction in kind or species.
How did Aristotle himself arrive at this list of causes? In chapter 3 he gives no indication, but later, in chapter 7, he notes that there are as many causes as there are specifically distinct "whys" of a thing.' In that case, however, the validity of the "whys" requires some justification.
Actually, Aristotle's theory of four causes appears to be a distillation of several convergent lines of philosophical inquiry. Aristotle had studied, and reached certain conclusions about, the conditions pertaining to generation or to becoming' He had also occupied himself with the principles of artistic creation, as witness the well-known example of the statue. And he had similarly made an analysis of the general methods of scientific investigation and explanation. The net result was his doctrine of four causes, which was further and finally confirmed through the process of comparing it with the corresponding investigations and findings of his predecessors.9 St. Thomas himself seems to suggest this train of development when he writes: "The Philosopher reduces all causes to the four modes which have been enumerated, saying that everything that is named cause falls under the aforesaid modes." 10
a) The intrinsic causes. - We have already seen that Aristotle identifies the essential principles of mobile being as matter and form. In propounding the theory of causes he reverts to these principles, declaring them, in effect, the intrinsic causes. Principles or causes, they are the same matter and form. But to designate them as "causes" adds to their notion a relation to the thing caused. This relation may be implied in a principle, too, but it is made more precise and explicit in the term "cause." Consequently, the terms "material cause" and "formal cause" give additional meaning respectively to the mere notions "matter" and "form."
Aristotle defines material cause as "that out of which a thing comes to be and which remains in it." 11 The Scholastic transliteration is:
ex quo aliquid fit cum insit.
To illustrate his definition Aristotle cites bronze, the material cause of the statue, and silver, the material cause of the bowl. Other examples are listed as occasion invites. Thus, letters of the alphabet are material causes of syllables; fire, earth, etc., of mixed bodies; parts, of the whole; premises, of the conclusion. Obviously, this type of causality presents itself in the most diversified areas of thought and reality, but always with the identical causal implication. In every case the thing or item in point is a cause on the ground of being a passive and immanent receptor of form, or, as the idiom has it, a cause in the manner of subject, "per modum subjecti."
Formal cause, on the other hand, Aristotle defines this way: "In another sense cause is the form or exemplar, that is, the definition of the essence and its genera." 12 The standard Scholastic formulation is:
id quo res determinatur ad certum essendi modum.13
Aristotle again illustrates. The parts of a definition, the ratio of 2 : 1 for an octave, and number generally, these are cited as instances of formal cause. Wherever the causal. ity of form is at work, its effect is to actualize the poten tiality of matter, or whatever assumes the role of matter.
Not to be overlooked is that Aristotle uses two different terms for formal cause: eidos and paradeigma. These are not synonymous. The first, "eidos," corresponds to formal cause in the proper sense, to the form intrinsic to a thing. The other, "paradeigma," denotes a model or exemplar, and is therefore called "exemplary cause." This kind of cause is extrinsic, but like formal cause it may serve to define a thing. Hence it assimilates to formal causality, and one speaks of it as "extrinsic formal cause," a notion which, though not to be gone into here, is far from negligible in Scholastic discussion.
Furthermore, something we referred to in the chapter on principles of mobile being may well be repeated here. Both material and formal causality have analogical applications. Primarily, it is true, material causality relates to prime matter and formal causality to substantial form. But, on another level, the reciprocal causality of matter and form exists between subjects and the accidents by which subjects are further determined. In grammar, too, and in logic and mathematics (still other fields could be mentioned) the same relationship, transferred, shows itself.
So much, for the moment, for material and formal cause, the intrinsic causes of mobile being.
b) The extrinsic causes. - Generation, or becoming of any kind, requires more than intrinsic causes. There has plainly to be a mover to initiate the process of becoming. And even this is not all. Necessary also, if we look closer, will be found the causal influence of an intended goal, which is to say, the end. Agent and end are therefore the extrinsic causes of change and, consequently, of mobile being itself.
In Aristotle's definition, efficient cause - perhaps "moving cause" would be more exact - is "the primary source of a change or coming to rest. Thus, the author of a decision is cause, the father is cause of the child, and in general anything that does the making of what is made and the changing of what is changed." 14 In Scholastic terms,
causa efficiens est principium a quo primo profluit motus.15
Efficient cause is what the average person usually means by cause." Philosophically, it is the primary principle, the headmost source, of any motion. Call it the point of departure, the terminus a quo, but remember it is more. Efficient cause is not passive; it exerts itself upon its subject, producing a real influx from agent to patient, the nature of which Thomistic commentators take much pains to clarify. As for the very existence of efficient causality, historically speaking Aristotle's assertion of it was partly in answer to Plato, who seems to have preferred to do without it and, in consequence, never managed to explain how forms make their way into matter.
Final cause, or end, is "that for the sake of which" an action takes place:
id cujus gratia aliquid fit.
In this way, says Aristotle, "health is the cause of walking. 'Why,' we ask 'does he walk?' For his health's sake.' And having said this, we think we have produced the cause." 17 If efficient cause is the most evident, final cause is often the most veiled and inscrutable. Not that its existence eludes the mind, but its precise working is most difficult to conceive. Aristotle notes that his predecessors scarcely suspected the existence of final cause." This is understandable, since it poses a number of thorny problems. How, for example, can final cause exert itself when it does not yet exist? And what of beings devoid of all power to know, nescient beings; how can they move themselves to an end? But most of all, does final cause really exist? Aware of these difficulties Aristotle, toward the end of Book II, gives the notion of final causality a thorough hauling over, which, however, nets its doubters and deniers nothing. Final cause, he cannot but aver, exists in nature." We shall have more to say on this later in the present chapter.
3. The Modes of Causes
Having established the division of causes, Aristotle follows it up with a division of their modes.20 We mentioned earlier that the differentiation of causes into their kinds is based on the diverse meanings or notions of cause itself (rationes causae). The diversification of their modes, on the other hand, is grounded on the different relationships that may exist between cause and effect. Hence, the modes do not constitute new kinds of causes.
Aristotle lists as many as twelve modes of cause. However, this number is got by dividing six modes by act and potency. The twelve, that is, may be cut to six. But the six themselves are reducible to three pairs of opposite members; which, in effect, means that the modalities of causes are basically three in number. A word about each will help to make this clear.
The first kind lists the modes per prius and per posterius. These terms correspond to anteriority and posteriority in the same line of causality. They may refer to the real order, or to the logical order of concepts. A more universal concept is anterior to a less universal. From this point of view a doctor is a "per posterius" cause of health, and the man (that he is) is a "per prius" cause, the notion of man being more universal than that of doctor. In the real order "per prius" and "per posterius" refer respectively to remote and proximate causes of real being. Thus, to use an ancient example, the proximate (per posterius) cause of a man's coming to be is another man, but the remote (per prius) cause is the sun.21
A second kind of modes couples the notions "essential" and "accidental." These, in Scholastic idiom, are the per se and per accidens modes. They indicate an essential or accidental association between cause and effect. For example, every effect has its proper (per se) cause. But both with the effect and with the cause may be associated modalities of being which, themselves, may also be regarded respectively as effects and causes. Polycleitus, in this respect, is accidentally (per accidens) the cause of the statue, since it might well have been carved by another sculptor. The proper (per se) cause is the statue-maker as such, whoever it may be. We shall see, presently, that accidental cause is highly important in the Aristotelian scheme of things, notably in the explanation of exceptional, that is, chance happenings.
The third kind of modes opposes simple and composite causes, simplex versus cornplexum. Aristotle again uses the example of Polycleitus-sculptor, which, together, constitute a composite cause of the statue, but taken separately are simple causes of it. A more concrete case of composite causality would be two forces actually harnessed together, say two horses on the same wagon.22
4. Aristotle's Causes: Network or Medley?
At first glance Aristotle's assemblage of causes may seem to be a gathering of disconnected notions, with apparently no unifying thread. Closer scrutiny, however, will show that this is far from the case. Even though, as we have said, there is not to be found a full-scale treatise on cause either in Aristotle or St. Thomas, both of them - St. Thomas even more so than Aristotle - present coordinated developments on the subject, and these, without exaggeration, add up to a truly integrated philosophy of cause.
Consider, first, the fact of four causes. This means that every mobile being is the work of four different causes, each exercising its proper causality in its own area of operation. So, in the case of the statue, bronze is the material cause; the figure carved into it, the formal cause; the sculptor, the efficient cause; and the purpose in its being made, the final cause. Thus, the four causes operate conjointly to produce, each in its own way, one and the same effect.
This is not all. The causes depend on each other for the exercise of their proper causality; which is the meaning of the axiom that causes are causes to each other: causae sunt ad invicem causae. Material and formal cause on the one hand, and efficient and final cause on the other, are associated pairs. Matter is not a cause except in conjunction with a formal cause; and the agent, if not determined or impelled by an end, cannot impart motion to anything. Since, moreover, matter and form cannot be brought into composition without an efficient cause, and this, as we have said, is itself conditioned and called into action by the end, the four causes are plainly so ordered as to constitute a closely knit economy, with final cause always in the commanding role. Seeing, therefore, how clearly Aristotle discerns and defines not only the kinds of causes but also their manifold interdependence, one has every right to speak of his thought in point, not as a medley, but as a philosophy or system of causes, a body of doctrine in which all parts are present and properly accounted for.
In the following passage from the Commentary on the Metaphysics St. Thomas summarizes the interconnection of causes with fine precision:
"Assuming, as previously established, that there are four causes, we should note that two of them have a reciprocal relation, and so do the other two. Efficient cause and end are reciprocally related in that efficient cause is the principle of motion, and end [final cause] the term. Similarly matter and form: form bestows existence and matter receives it. Efficient cause is therefore cause of the end, and the end is cause of efficient cause. Efficient cause is cause of the end as to its existence, since by its activity efficient cause brings the end into being. The end, on the other hand, is cause of efficient cause, not as to its existence, but as the reason [ratio] of its causality. For, efficient cause is cause so far as it acts, but it does not act except by reason of the end. Hence, efficient cause has its causality from the end. Form and matter, however, are causes of each other as to their existence: form of matter, in that form causes matter to be in act; but matter of form, in that it sustains form." 23
And in this other passage from the same Commentary St. Thomas declares the priority and pre-eminence of final cause:
"Although in some things the end is last with respect to existence, in the order of causality it is always first. Hence it is called the cause of causes, since it is cause of the causality of all causes. It is cause of the causality of efficient cause, as already said. Efficient cause, in turn, is cause of the causality of matter and form, for by its activity it causes matter to be receptive of form, and form to inhere in matter. Therefore the end is also cause of the causality of matter and form." 24
As we shall see in the course of this chapter, and indeed of our study, Aristotle's whole procedure in natural philosophy, his every argument and demonstration, is governed by this hierarchical concept of causes, in which, once more, the primacy is always to final cause.25