Chapter XIII. Causality; Classification Of Causes.
94. Traditional Concept of Cause.—The modes of real being which we have been so far examining—substance, quality, quantity, relation—are modes of reality considered as static. But it was pointed out in an early chapter (ch. [ii.]) that the universe of our experience is subject to change, that it is ever becoming, that it is the scene of a continuous world-process which is apparently regulated by more or less stable principles or laws, these laws and processes constituting the universal order which it is the duty of the philosopher to study and explain. We must now return to this kinetic and dynamic aspect of reality, and investigate the principles of change in things by a study of Causes.
As with the names of the other ultimate categories, so too here, the general sense of the term “cause” (causa, αἴτιον) is familiar to all, while analysis reveals a great variety of modalities of this common signification. We understand by a cause anything which has a positive influence of any sort on the being or happening of something else. In philosophy this is the meaning which has been attached traditionally to the term since the days of Aristotle; though in its present-day scientific use the term has almost lost this meaning, mainly through the influence of modern phenomenism.[434] The traditional notion of cause is usually expounded by comparing it with certain kindred notions: principle, condition, occasion, reason.
A principle is that from which anything proceeds in any way whatsoever.[435] Any sort of intrinsic connexion between two [pg 358] objects of thought is sufficient to constitute the one a “principle” of the other; but a mere extrinsic or time sequence is not sufficient. A logical principle is some truth from which further truths are or may be derived. A real principle is some reality from which the being or happening of something originates and proceeds.[436] If this procession involves a real and positive influence of the principle on that which proceeds from it, such a real principle is a cause. But there may be a real and intrinsic connexion without any such influence. For instance, in the substantial changes which occur in physical nature the generation of the new substantial formative principle necessarily presupposes the privation of the one which antecedently “informed” the material principle; but this “privatio formae” has no positive influence on the generation of the new “form”; it is, however, the necessary and natural antecedent to the generation of the latter; hence although this “privatio formae” is a real principle of substantial change (the process or fieri) it is not a cause of the latter. The notion of principle, even of real principle, is therefore wider than the notion of cause.[437]
A condition, in the proper sense of a necessary condition or conditio sine qua non, is something which must be realized or fulfilled before the event or effect in question can happen or be produced. On the side of the latter there is real dependence, but from the side of the former there is no real and positive influence on the happening of the event. The influence of the condition is negative; or, if positive, it is only indirect, consisting in the removal of some obstacle—“removens probibens”—to the positive influence of the cause. In this precisely a condition differs from a cause: windows, for instance, are a condition for the lighting of a room in the daylight, but the sun is the cause. The distinction is clear and intelligible, nor may it be ignored in [pg 359] a philosophical analysis of causality. At the same time it is easy to understand that where, as in the inductive sciences, there is question of discovering all the antecedents, positive and negative, of any given kind of phenomenon, in order to bring to light and formulate the law or laws according to which such phenomenon occurs, the distinction between cause and condition is of minor importance.[438]
An occasion is any circumstance or combination of circumstances favourable to the action of a free cause. For instance, a forced sale is an occasion for buying cheaply; night is an occasion of theft; bad companionship is an occasion of sin. An occasion has no intrinsic connexion with the effect as in the case of a principle, nor is it necessary for the production of the effect as in the case of a condition. It is spoken of only in connexion with the action of a free cause; and it differs from a cause in having no positive and direct influence on the production of the effect. It has, however, a real though indirect influence on the production of the effect by soliciting and aiding the determination of the free efficient cause to act. In so far as it does exert such an influence it may be regarded as a partial efficient cause, not a physical but a moral cause, of the effect.
To ask for the reason of any event or phenomenon, or of the nature or existence of any reality, is to demand an explanation of the latter; it is to seek what accounts for the latter, what makes this intelligible to our minds. Whatever is a cause is therefore also a reason, but the latter notion is wider than the former. Whatever explains a truth is a logical reason of the latter. But since all truths are concerned with realities they must have ultimately real reasons, i.e. explanatory principles inherent in the realities themselves. The knowledge of these real or ontological principles of things is the logical reason of our understanding of the things themselves. But the ontological principles, which are the real reasons of the things, are wider in extent than the causes of these things, for they include principles that are not causes.
Furthermore, the grades of reality which we discover in things by the activity of abstract thought, and whereby we compare, classify and define those things, we apprehend as explanatory principles of the latter; and these principles, though really in the things, and therefore real “reasons,” are not “causes”.
Thus, life is a real reason, though not a cause, of sensibility in the animal organism; the soul's independence of matter in its mode of existence is a real reason, though not a cause, of its spiritual activities. Hence, between a reason and that which it accounts for there may be only a logical distinction, while between a cause and that which it causes there must be a real distinction ([38]).
To understand all the intrinsic principles which constitute the essence of anything is to know the sufficient reason of its reality. To understand all the extrinsic principles which account for its actual existence is to know the sufficient reason of its existence; and to understand this latter adequately is to realize that the thing depends ultimately for its actual existence on a Reality or Being which necessarily exists by virtue of its own essence.
What has been called the Principle of Sufficient Reason asserts, when applied to reality, that every existing reality must have a sufficient reason for existing and for being what it is.[439] Unlike the Principle of Causality which is an axiomatic or self-evident truth, this principle is rather a necessary postulate of all knowledge, an assumption that reality is intelligible. It does not mean that all reality, or even any single finite reality, is adequately intelligible to our finite minds. In the words of Bossuet, we do not know everything about anything: “nous ne savons le tout de rien”.
In regard to contingent essences, if these be composite we can find a sufficient reason why they are such in their constitutive principles; but in regard to simple essences, or to the simple constitutive principles of composite essences, we can find no sufficient reason why they are such in anything even logically distinct from themselves: they are what they are because they are what they are, and to demand why they are what they are, is, as Aristotle remarked, to ask an idle question. At the same time, when we have convinced ourselves that their actual existence involves the existence of a Supreme, Self-Existent, Intelligent Being, we can see that the essence of this Being is the ultimate ground of the intrinsic possibility of all finite essences ([20]).
In regard to contingent existences the Principle of Sufficient Reason is coincident with the Principle of Causality, inasmuch as the sufficient reason of the actual existence of any contingent thing consists in the extrinsic real principles which are its causes. The existence of contingent things involves the existence of a Necessary Being. We may say that the sufficient reason for the existence of the Necessary Being is the Divine Essence Itself; but this is merely denying that there is outside this Being any sufficient reason, i.e. any cause of the latter's existence; it is the recognition that the Principle of Causality is inapplicable to the Necessary Being. The Principle of Sufficient Reason, in this application of it, is logically posterior to the Principle of Causality.[440]
95. Classification of Causes: Aristotle's Fourfold Division.—In modern times many scientists and philosophers have thought it possible to explain the order and course of nature, the whole cosmic process and the entire universe of our experience, by an appeal to the operation of efficient causes. Espousing a mechanical, as opposed to a teleological, conception of the universe, they have denied or ignored all influence of purpose, and eschewed all study of final causes. Furthermore, misconceiving or neglecting the category of substance, and the doctrine of substantial change, they find no place in their speculations for any consideration of formal and material causes. Yet without final, formal and material causes, so fully analysed by Aristotle[441] and the scholastics, no satisfactory explanation of the world of our experience can possibly be found. Let us therefore commence by outlining the traditional fourfold division of causes.
We have seen already that change involves composition or compositeness in the thing that is subject to change. Hence two intrinsic principles contribute to the constitution of such a thing, the one a passive, determinable principle, its material cause, the other an active, determining principle, its formal cause. Some changes in material things are superficial, not reaching to the substance itself of the thing; these are accidental, involving the union of some accidental “form” with the concrete pre-existing substance as material (materia “secunda”). Others are more profound, changes of the substance itself; these are substantial, involving the union of a new substantial “form” with the primal material principal (materia “prima”) of the substance undergoing the change. But whether the change be substantial or accidental we can always distinguish in the resulting composite thing two intrinsic constitutive principles, its formal cause and its material cause. The agencies in nature which, by their activity, bring about change, are efficient causes. Finally, since it is an undeniable fact that there is order in the universe, that its processes give evidence of regularity, of operation according to law, that the cosmos reveals a harmonious co-ordination of manifold agencies and a subordination of means to ends, it follows that there must be working in and through all nature a directive principle, a principle of plan or design, a principle according to which those manifold agencies work together in fulfilment of a [pg 362] purpose, for the attainment of ends. Hence the reality of a fourth class of causes, final causes.
The separate influence of each of those four kinds of cause can be clearly illustrated by reference to the production of any work of art. When, for instance, a sculptor chisels a statue from a block of marble, the latter is the material cause (materia secunda) of the statue, the form which he induces on it by his labour is the formal cause (forma accidentalis), the sculptor himself as agent is the efficient cause, and the motive from which he works—money fame, esthetic pleasure, etc.—is the final cause.
The formal and material causes are intrinsic to the effect; they constitute the effect in facto esse, the distinction of each from the latter being an inadequate real distinction. It is not so usual nowadays to call these intrinsic constitutive principles of things causes of the latter; but they verify the general definition of cause. The other two causes, the efficient and the final, are extrinsic to the effect, and really and adequately distinct from it,[442] extrinsic principles of its production, its fieri.
This classification of causes is adequate;[443] it answers all the questions that can be asked in explanation of the production of any effect: a quo? ex quo? per quid? propter quid? Nor is there any sort of cause which cannot be brought under some one or other of those four heads. What is called an “exemplar cause,” causa exemplaris, i.e. the ideal or model or plan in the mind of an intelligent agent, according to which he aims and strives to execute his work, may be regarded as an extrinsic formal cause; or again, in so far as it aids and equips the agent for his task, an efficient cause; or, again, in so far as it represents a good to be realized, a final cause.[444]
The objects of our knowledge are in a true sense causes of our knowledge: any such object may be regarded as an efficient cause, both physical and moral, of this knowledge, in so far as by its action on our minds it determines the activity of our cognitive faculties; or, again, as a final cause, inasmuch as it is the end and aim of the knowledge.
The essence of the soul is, as we have seen ([69]), not exactly an efficient cause of the faculties which are its properties; but it is their final cause, inasmuch as their raison d'être is to perfect it; and their subjective or material cause, inasmuch as it is the seat and support of these faculties.
The fourfold division is analogical, not univocal: though the matter, the form, the agent, and the end or purpose, all contribute positively to the production of the effect, it is clear that the character of the causal influence is widely different in each case.
Again, its members do not demand distinct subjects: all four classes of cause may be verified in the same subject. For instance, the human soul is a formal cause in regard to the composite human individual, a material cause in regard to its habits, an efficient cause in regard to its acts, and a final cause in regard to its faculties.
Furthermore, the fourfold division is not an immediate division, for it follows the division of cause in general into intrinsic and extrinsic causes. Finally, it is a division of the causes which we find to be operative in the universe. But the philosophical study of the universe will lead us gradually to the conviction that itself and all the causes in it are themselves contingent, themselves caused by and dependent on, a Cause outside or extrinsic to the universe, a First, Uncaused, Uncreated, Self-Existent, Necessary Cause (Causa Prima, Increata), at once the efficient and final cause of all things. In contrast with this Uncreated, First Cause, all the other causes we have now to investigate are called created or second causes (causae secundae, creatae).
A cause may be either total, adequate, or partial, inadequate, according as the effect is due to its influence solely, or to its influence in conjunction with, or dependence on, the influence of some other cause or causes of the same order. A created cause, therefore, is a total cause if the effect is due to its influence independently of other created causes; though of [pg 364] course all created causes are dependent, both as to their existence and as to their causality, on the influence of the First Cause. Without the activity of created efficient and final causes the First Cause can accomplish directly whatever these can accomplish—except their very causality itself, which cannot be actualized without them, but for which He can supply eminenter. Similarly, while it is incompatible with His Infinite Perfection that He discharge the function of material or formal cause of finite composite things, He can immediately create these latter by the simultaneous production (ex nihilo) and union of their material and formal principles.
A cause is said to be in actu secundo when it is actually exercising its causal influence. Antecedently to such exercise, at least prioritate naturae, it is said to be in actu primo: when it has the expedite power to discharge its function as cause it is in actu primo proximo, while if its power is in any way incomplete, hampered or unready, it is in actu primo remoto.
Many other divisions of cause, subordinate to the Aristotelian division, will be explained in connexion with the members of this latter.
96. Material and Formal Causes.—These are properly subject-matter for Cosmology. We will therefore very briefly supplement what has been said already concerning them in connexion with the doctrine of Change (ch. [ii.]). By a material cause we mean that out of which anything is made: id ex quo aliquid fit. Matter is correlative with form: from the union of these there results a composite reality endowed with either essential or accidental unity—with the former if the material principle be absolutely indeterminate and the correlative form substantial, with the latter if the material principle be some actually existing individual reality and the form some supervening accident. Properly speaking only corporeal substances have material causes,[445] but the term “material cause” is used in an extended sense to signify any potential, passive, receptive subject of formative or actuating principles: thus the soul is the subjective or material cause of its faculties and habits; essence of existence; genus of differentia, etc.
In what does the positive causal influence of a material cause consist? How does it contribute positively to the actualization of the composite reality of which it is the material cause? It receives and unites with the form which is educed from its potentiality by the action of efficient causes, and thus contributes to the generation of the concrete, composite individual reality.[446]
It is by reason of the causality of the formal cause that we speak of a thing being formally such or such. As correlative of material cause it finds its proper application in reference to the constitution of corporeal things. The formative principle, called forma substantialis, which actuates, determines, specifies the material principle, and by union with the latter constitutes an individual corporeal substance of a definite kind, is the (substantial) formal cause of this composite substance.[447] The material principle of corporeal things is of itself indifferent to any species of body; it is the form that removes this indefiniteness and determines the matter, by its union with the latter, to constitute a definite type of corporeal substance.[448] The existence of different species of living organisms and different types of inorganic matter in the universe implies in the constitution of these things a common material principle, materia prima, and a multiplicity of differentiating, specifying, formative principles, formae substantiales. That the distinction between these two principles in the constitution of any individual corporeal substance, whether living or inorganic, is not merely a virtual distinction between metaphysical (generic and specific) grades of being in the individual, but a real distinction between separable entities, is a scholastic thesis established in the Special Metaphysics of the organic and inorganic domains of the universe.[449]
Since the form is a perfecting, actuating principle, the term is often used synonymously with actus, actuality. And since besides the essential perfection which a being has by virtue of its substantial form it may have accidental perfections by reason of supervening accidental forms, these, too, are formal causes.
In what does the causal influence of the formal cause consist? In communicating itself intrinsically to the material principle or passive subject from whose potentiality it is evoked by the action of efficient causes; in actuating that potentiality by intrinsic union therewith, and thus determining the individual subject to be actually or formally an individual of such or such a kind.
The material and formal causes are intrinsic principles of the constitution of things. We next pass to an analysis of the two extrinsic causes, and firstly of the efficient cause and its causality.
97. Efficient Cause; Traditional Concept Explained.—By efficient cause we understand that by which anything takes place, happens, occurs: id a quo aliquid fit. The world of our external and internal experience is the scene of incessant changes: men and things not only are, but are constantly becoming. Now every such change is originated by some active principle, and [pg 367] this we call the efficient cause of the change. Aristotle called it τὸ κινητικόν or ἡ ἀρχὴ κινητική, the kinetic or moving principle; or again, ἀρχὴ κινησέως ἢ μεταβολῆς ἐν ἑτέρω, principium motus vel mutationis in alio, “the principle of motion or change in some other thing”. The result achieved by this change, the actualized potentiality, is called the effect; the causality itself of the efficient cause is called action (ποίησις), motion, change—and, from the point of view of the effect, passio (παθήσις). The perfection or endowment whereby an efficient cause acts, i.e. its efficiency (ἐνέργεια), is called active power (potentia seu virtus activa); it is also called force or potential energy in reference to inanimate agents, faculty in reference to animate agents, especially men and animals. This active power of an efficient cause or agent is to be carefully distinguished from the passive potentiality acted upon and undergoing change. The former connotes a perfection, the latter an imperfection: unumquodque agit inquantum est in actu, patitur vero inquantum, est in potentia. The scope of the active power of a cause is the measure of its actuality, of its perfection in the scale of reality; while the extent of the passive potentiality of patiens is a measure of its relative imperfection. The actuation of the former is actio, that of the latter passio. The point of ontological connexion of the two potentiae is the change (motus, κίνησις), this being at once the formal perfecting of the passive potentiality in the patiens or effect, and the immediate term of the efficiency or active power of the agens or cause. Actio and passio, therefore, are not expressions of one and the same concept; they express two distinct concepts of one and the same reality, viz. the change: actio et passio sunt idem numero motus. This change takes place formally in the subject upon which the efficient cause acts, for it is an actuation of the potentiality of the former under the influence of the latter: ἡ κίνησις ἐν τῷ κινητῷ; ἐντελέχεια γὰρ ἐστι τόυτου. Considered in the potentiality of this subject—“τὸ τοῦδέ ἐν τῷδε: hujus in hococ”—it is called passio. Considered as a term of the active power of the cause—“τοῦδε ὑπο τοῦδε: hujus per hoc”—it is called actio.
The fact that actio and passio are really and objectively one and the same motus does not militate against their being regarded as two separate supreme categories, for they are objects of distinct concepts,[450] and this is sufficient to constitute them distinct categories ([60]).
Doubts are sometimes raised, as St. Thomas remarks,[451] about the assertion that the action of an agent is not formally in the latter but in the patiens: actio fit in passo. It is clear, however, he continues, that the action is formally in the patiens for it is the actuation not of any potentiality of the agent, but of the passive potentiality of the patiens: it is in the latter that the motus or change, which is both actio and passio, takes place, dependently of course on the influence of the agent, or efficient cause of the change. The active power of an efficient cause is an index of the latter's actuality; the exercise of this power (i.e. action) does not formally perfect the agent, for it is not an actuation of any passive potentiality of the latter; it formally perfects the patiens. Only immanent action perfects the agent, and then not as agent but as patiens or receiver of the actuality effected by the action (cf. [103] infra).
We may, then, define efficient cause as the extrinsic principle of the change or production of anything by means of action: principium extrinsicum a quo fluit motus vel productio rei mediante actione.
It is a “first” principle as compared with material and formal causes for its influence is obviously prior in nature to theirs; also as compared with the other extrinsic cause, the final cause, in ordine executionis, not, however, in ordine intentionis. The “end,” not as realized but as realizable, not in execution but in intention, discharges its function and exerts its influence as “final cause” and in this order the final cause, as will appear later, is the first of all causes: finis est ultimus in executione sed primus in intentione.
“Change or production,” in the definition, is to be understood not in the strict sense in which it presupposes an existing [pg 369] subject or material, but in the wide sense in which it includes any production of new reality, even creation or production ex nihilo.
“Action,” too, is to be understood in the wide sense in which it includes the action of the First Cause, which action is really identical with the essence of the latter. We conceive creation after the analogy of the efficient action of created or “second” causes: we have no proper concept of the infinite perfection of the Divine activity. In all created efficient causes not only is the action itself, but also the efficiency, force, power, faculty, which is its proximate principle, really distinct from the nature or essence of the agent; the former is a substance, the latter an accident.
Finally, the action of a created efficient cause is either transitive (transiens) or immanent (immanens) according as the change wrought by the action takes place in something else (as when the sun heats or lights the earth) or in the cause itself (as when a man reasons or wills). In the former case the action perfects not the agent but the other thing, the patiens; in the latter case it perfects the agent itself, agens and patiens being here the same identical concrete individual.[452]
98. Some Scholia on Causation. the Principle Of Causality.—Before enumerating the principal kinds of efficient cause, and analysing the nature of efficient causality, we may set down here certain self-evident axioms and aphorisms concerning causation in general. (a) The most important of these is the Principle of Causality, which has been enunciated in a variety of ways: Whatever happens has a cause; Whatever begins to be has a cause; Whatever is contingent has a cause; Nothing occurs without a cause. Not everything that begins to be has necessarily a material cause, or a formal cause, really distinct from itself. For instance, simple spiritual beings, like the human soul, have no material cause, nor any formal cause or constitutive principle distinct from their essence. Similarly, the whole universe, having been created ex nihilo, had no pre-existing material cause. All the material beings, however, which are produced, generated, brought into actual existence in the course of the incessant changes which characterize the physical universe, have both material and [pg 370] formal causes. But the Principle of Causality refers mainly to extrinsic causes. It is commonly understood only of efficient causes; and only in regard to these is it self-evident. We shall see that as a matter of fact nothing happens without a final cause: that intelligent purpose pervades reality through and through. This, however, is a conclusion, not a principle. What is really a self-evident, axiomatic, necessary principle is that whatever happens has an efficient cause. Only the Necessary, Self-Existing, Eternal Being, has the sufficient reason of His actual existence in Himself, in His own essence. That any being which is contingent could exist independently of some other actual being as the cause of this existence; that it could have come into existence or begun to exist from absolute nothingness, or be produced or brought into actual existence without any actual being to produce it; or that, once existing and subject to change, it could undergo change and have its potentialities actualized without any actual being to cause such change ([10])—all this is positively unthinkable and absolutely repugnant to our intelligence; all this our reason peremptorily declares to be intrinsically impossible. Nor is there question of a mere psychological inconceivability, such as might be due to a long-continued custom of associating the idea of a “beginning” with the idea of a “cause” of this beginning—as phenomenists generally contend.[453] There is question of an impossibility which our reason categorically dictates to be a real, ontological impossibility. The Principle of Causality is therefore a necessary, a priori, self-evident principle.
(b) Every effect must have an adequate efficient cause, i.e. a [pg 371] cause sufficiently perfect, sufficiently high on the scale of being, to have the active power to produce the effect in question; otherwise the effect would be partially uncaused, which is impossible.
(c) An effect cannot as such be actually more perfect than its adequate (created) cause. The reason is that the effect as such is really dependent for its actuality on its adequate created cause. It derives its actuality from the latter. Now it is inconceivable that an agent could be the active, productive principle of a greater perfection, a higher grade of actuality, than itself possesses. Whatever be the nature of efficient causality, actio and passio ([102]), or of the dependence of the produced actuality upon the active power of its adequate efficient cause ([10]), the reality of this dependence forbids us to think that in the natural order of efficient causation a higher grade of reality can be actualized than the agent is capable of actualizing, or that the agent can naturally actualize a higher or more perfect grade of reality than is actually its own. We must, however, bear in mind that there is question of the adequate created cause of an effect; and that to account fully for the actualization of any potential reality whatsoever we are forced to recognize in all causation of created efficient causes the concursus of the First Cause.
(d) The actuality of the effect is in its adequate created cause or causes, not actually and formally, but potentially or virtually. If the cause produce an effect of the same kind as itself (causa univoca), as when living organisms propagate their species, the perfection of the effect is said to be in the cause equivalently (aequivalenter); if it produce an effect of a different kind from itself (causa analoga), as when a sculptor makes a statue, the perfection of the effect is said to be in the cause eminently (eminenter).
(e) Omne agens agit inquantum est in actu. The operative power of a being is in proportion to its own actual perfection: the higher an agent is on the scale of reality, or in other words the more perfect its grade of being, the higher and more perfect will be the effects achieved by the exercise of its operative powers. In fact our chief test of the perfection of any nature is [pg 372] analysis of its operations. Hence the maxim so often referred to already:—
(f) Operari sequitur esse; qualis est operatio talis est natura; modus operandi sequitur modum essendi. Operation is the key to nature; we know what any thing is by what it does.
(g) Nihil agit ultra suam speciem; or, again, Omne agens agit simile sibi. These are inductive generalizations gathered from experience, and have reference to the natural operation of agents, especially in the organic world. Living organisms reproduce only their own kind. Moreover, every agency in the universe has operative powers of a definite kind; acting according to its nature it produces certain effects and these only; others it cannot produce: this is, in the natural order of things, and with the natural concursus of the First Cause. But created causes have a passive obediential capacity (potentia obedientialis) whereby their nature can be so elevated by the First Cause that they can produce, with His special, supernatural concursus, effects of an entirely higher order than those within the ambit of their natural powers.[454]
(h) From a known effect, of whatsoever kind, we can argue with certainty, a posteriori, to the existence of an adequate efficient cause, and to some knowledge of the nature of such a cause.[455] By virtue of the principle of causality we can infer the existence of an adequate cause containing either equivalently or eminently all the perfections of the effect in question.
99. Classification of Efficient Causes.—(a) We have already referred to the distinction between the First Cause and Second or Created Causes. The former is absolutely independent of all other beings both as to His power and as to the exercise of this power. The latter are dependent, for both, upon the former.
The distinction between a first, or primary, or independent cause, and second, or subordinate, or dependent causes can be understood not only of causes universally, but also as obtaining among created causes themselves. In general the subordination of a cause to a superior or anterior cause may be either essential or accidental: essential, when the second cause depends—either for its existence or for an indispensable complement of its [pg 373] efficiency—on the present actual influence of the other cause; accidental when the second cause has indeed received its existence or efficiency from this other cause, but is now no longer dependent, for its existence or action, on the latter. Thus, living organisms are, as causes, accidentally subordinate to their parent organisms: they derived their existence from the latter, but are independent of these when in their maturity they continue to exist, and live, and act of themselves and for themselves. But all creatures, on the other hand, are, as causes, essentially subordinate to the Creator, inasmuch as they can exist and act only in constant dependence on the ever present and ever actual conserving and concurring influence of the Creator.
It is obvious that all the members of any series of causes essentially subordinate the one to the other must exist simultaneously. Whether such a series could be infinite depends, therefore, on the question whether an actually infinite multitude is intrinsically possible. This difficulty cannot be urged with such force against an infinite regress in causes accidentally subordinate to one another; for here such a regress would not involve an actually infinite multitude of things existing simultaneously. In the case of essentially subordinate causes, moreover, the series, whatever about its infinity, must contain, or rather imply above it, one cause which is first in the sense of being independent, or exempt from the subordination characteristic of all the others. And the reason is obvious: Since no one of them can exist or act except dependently on another, and this on another, and so on, it is manifest that the series cannot exist at all unless there is some one cause which, unlike all the others, exists and acts without such subordination or dependence. Hence, in essentially subordinate causes an infinite regress is impossible.[456] In Natural Theology these considerations are of supreme importance.
(b) An efficient cause may be described as immanent or transitive according as the term of its action remains within the cause itself, or is produced in something else. The action of the First Cause is formally immanent, being identical with the Divine Nature itself; it is virtually transitive when it is creative, or operative among creatures.
(c) An efficient cause is either a principal or an instrumental cause. When two causes so combine to produce an effect that [pg 374] one of them uses the other the former is called the principal and the latter the instrumental cause. Thus I am the principal cause of the words I am writing; my pen is the instrumental cause of them. Such an effect is always attributed to the principal cause, not to the instrumental. The notion of an instrument is quite a familiar notion. An instrument helps the principal agent to do what the latter could not otherwise do, or at least not so easily. An instrument therefore is really a cause. It contributes positively to the production of the effect. How does it do so? By reason of its nature or structure it influences, modifies, and directs in a particular way, the efficiency of the principal cause. But this property of the instrumental cause comes into play only when the latter is being actually used by a principal cause. A pen, a saw, a hammer, a spade, have each its own instrumentality. The pen will not cut, nor the saw mould iron, nor the hammer dig, nor the spade write, for the agent that uses them. Each will produce its own kind of effect when used; but none of them will produce any effect except when used: though each has in itself permanently and inherently the power to produce its own proper effect in use.[457] We have instanced the use of artificial instruments. But nature itself provides some agencies with what may be called natural instruments. The semen whereby living organisms propagate their kind is an instance. In a less proper sense the various members of the body are called instruments of the human person as principal cause, “instrumenta conjuncta”.
The notion of an instrumental cause involves then (a) subordination of the latter, in its instrumental activity, to a principal cause, (b) incapacity to produce the effect otherwise than by modifying and directing the influence of the principal cause. This property whereby the instrumental cause modifies or determines in a particular way the influence of the principal cause, is called by St. Thomas an actio or operatio of the former; the distinction between the principal and the instrumental cause being that whereas the former acts by virtue of a power permanently inherent in it as a natural perfection, the latter acts as an instrument [pg 375] only by virtue of the transient motion which it derives from the principal cause which utilizes it.[458]
We may, therefore, define an instrumental cause as one which, when acting as an instrument, produces the effect not by virtue of its inherent power alone, but by virtue of a power communicated to it by some principal cause which acts through it. A principal cause, on the other hand, is one which produces its effect by virtue of an active power permanently inherent in itself.
The designations principal and instrumental are obviously correlative. Moreover, all created causes may be called instrumental in relation to the First Cause. For, not only are they dependent on the latter for the conservation of their nature and active powers; they are also dependent, in their action, in their actual exercise of these powers, on the First Cause (for the concursus of the latter).[459] Yet some created causes have these powers [pg 376] permanently, and can exercise them without subordination to other creatures; while others need, for the exercise of their proper functions, not only the Divine concursus, but also the motion of other creatures. Hence the former are rightly called principal created causes, and the latter instrumental created causes.
(d) Efficient causes are divided into free causes and necessary causes. A free or self-determining cause is one which is not determined by its nature to one line of action, but has the power of choosing, or determining itself, to act or abstain, when all the conditions requisite for acting are present. Man is a free agent, or free cause, of his deliberate actions. A necessary cause, or natural cause as it is sometimes called, is one which is determined by its nature to one invariable line of action, so that, granted the conditions requisite for action, it cannot naturally abstain from acting in that invariable manner. All the physical agencies of the inorganic world, all plant and animal organisms beneath man himself, are necessary causes.
The freedom of the human will is established against determinism in Psychology.[460] The difficulties of determinists against this doctrine are for the most part based on misconceptions, or on erroneous and gratuitous assumptions. We may mention two of them here.[461] Free activity, they say, would be causeless activity: it would violate the “law of universal causation”. We reply that free activity is by no means causeless activity. The free agent himself is in the fullest and truest sense the efficient cause of his free acts. It is by his causal, efficient influence that the act of free choice is determined and elicited. Free causality evidently does not violate the necessary, a priori principle set forth above under the title of the Principle of Causality. But—they urge in the second place—it violates the “law of universal causation,” i.e. the law that every event in nature must be the result of some set of phenomenal antecedents which necessitate it, and which, therefore, whenever verified, must produce this result and no other; and by violating this law it removes all supposed “free” activities from the domain of that regularity [pg 377] and uniformity without which no scientific knowledge of such phenomena would be possible. To this we reply, firstly, that the law of uniform causation in nature, the law which is known as the “Law of the Uniformity of Nature,” and which, under the title of the “Law of Universal Causation” is confounded by determinists and phenomenists with the entirely distinct “Principle of Causality”—is not by any means a law of necessary causation.[462] The statement that Nature is uniform in its activities is not the expression of an a priori, necessary truth, like the Principle of Causality. It is a generalization from experience. And experience testifies to the existence of grades in this all-prevailing uniformity. In the domain of physical nature it is the expression of the Free Will of the Author of Nature, who may miraculously derogate from this physical uniformity for higher, moral ends. In the domain of deliberate human activities it is the expression of that less rigorous but no less real uniformity which is dependent on the free will of man. And just as the possibility of miracles in the former domain does not destroy the regularity on which the generalizations of the physical sciences are based, so neither does the fact of human free will render worthless or unreliable the generalizations of the human sciences (ethical, social, political, economic, etc.) about human conduct. Were the appearance of miracles in the physical domain, or the ordinary play of free will in the human domain, entirely capricious, motiveless, purposeless, the results would, of course, be chaotic, precarious, unaccountable, unintelligible, and scientific knowledge of them would be impossible: for the assumption that reality is the work of intelligent purpose, and is therefore a regular, orderly expression of law, in other words, the assumption that the universe is intelligible, is a prerequisite condition for scientific knowledge about the universe. But determinists seem to assume that Divine Providence and human free will must necessarily imply that the whole universe of physical phenomena and human activities would be an unintelligible chaos; and having erected this philosophical scarecrow on a gratuitous assumption they think it will gradually exorcise all belief in Divine Providence and human freedom from the “scientific” mind!
(e) Efficient causes are either physical or moral. A physical efficient cause is one which produces its effect by its own proper power and action—whether immediately or by means of an instrument. [pg 378] For instance, the billiard player is the physical cause of the motion he imparts to the balls by means of the cue. A moral cause is one which produces its effect by the representation of something as good or evil to the mind of a free agent; by inducing the latter through example, advice, persuasion, promises, threats, commands, entreaties, etc., to produce the effect in question. For instance, a master is the moral cause of what his servant does in obedience to his commands. The motives set forth by way of inducement to the latter are of course final causes of the latter's action. But the former, by setting them forth, is the moral cause of the action: he is undoubtedly more than a mere condition; he contributes positively and efficiently to the effect. His physical causation, however, does not reach to the effect itself, but only to the effect wrought in the mind of the servant by his command. It is causally connected with the physical action of the servant by means of an intermediate link which we may call mental or psychical causation—actio “intentionalis,”—the action of cognition on the mind of a cognitive agent.
The agent employed by a moral cause to produce an effect physically may be called an instrumental cause in a wide and less proper sense of this term, the instrumentality being moral, not physical. Only free agents can be moral causes; and as a rule they are termed moral causes only when they produce the effect through the physical operation of another free agent. What if they employ not free agents, nor yet inanimate instruments, but agents endowed with sense cognition and sense appetite, to produce effects? If a man set his dog at another, is he the moral or the physical cause of the injuries inflicted by the dog? That he is the principal efficient cause is unquestionable. But is he the principal physical cause and the dog the instrument? We think it is more proper to call the principal efficient cause a moral cause in all cases where there intervenes between his physical action and the effect an intermediate link of “psychical” or “intentional” action, even though, as in the present example, this psychical link is of the sentient, not the intellectual, order.
(f) The efficient cause, like other causes, may be either partial or total, according as it produces the effect by co-operation with other causes, or by itself alone. The aim of the inductive sciences is to discover for each kind of natural event or phenomenon the “total cause” in the comprehensive sense of the whole group of positive agencies or causes proper, and negative antecedent and [pg 379] concomitant conditions which are indispensable and necessitating principles of the happening of such kind of event.[463]
(g) We can distinguish between the immediate or determining, the more or less proximate, and the more or less remote, efficient causes of an event. Thus, the application of the fuse to the charge of dynamite in a rock is the immediate or determining cause of the explosion which bursts the rock; the lighting of the fuse, the placing of the charge, etc., the more proximate causes; the making of the fuse, dynamite, instruments, etc., the more remote causes. Again the aim of the inductive sciences is to discover the “total proximate cause” of events,[464] leaving the investigation of ultimate causes, as well as the analysis of causality itself, to philosophy.
(h) Finally, we must distinguish between the individual agent itself as cause (the suppositum or person that acts); the agent's nature and active power as causes; and the action, or exercise of this power as cause. The former, the individual, concrete agent, is the “principium quod agit,” and is called the “causa ut quae”. The nature and the active power of the agent are each a “principium quo agens agit,” the remote and the proximate principle of action respectively; and each is called a “causa ut qua”. The action of the agent is the cause of the effect in the sense that the actual production or fieri of anything is the immediate cause of this thing in facto esse. Corresponding to these distinctions we distinguish between the cause in actu primo remoto, in actu primo proximo, and in actu secundo. These distinctions are of no little importance. By ignoring them, and by losing sight of the intrinsic (formal and material) causes of natural phenomena, many modern scientists and philosophers have confounded cause and effect with the process itself of causation, and declared that cause and effect are not distinct realities, but only two mental aspects of one and the same reality.[465]
The same may be said of all the distinctions so far enumerated. They are absolutely essential to the formation of clear ideas on the question of causality. No term in familiar use is of more profound philosophical significance, and at the same time more elastic and ambiguous in its popular meanings, than the term cause. This is keenly felt in the Logic of the Inductive Sciences, where not only the discovery, but the exact measurement, of physical causes, is the goal of research.
“When we call one thing,” writes Mr. Joseph,[466] “the cause of another, the real relation between them is not always the same.... We say that [pg 380] molecular action is the cause of heat, that the heat of the sun is the cause of growth, that starvation is sometimes the cause of death, that jealousy is a frequent cause of crime. We should in the first case maintain that cause and effect are reciprocally necessary; no heat without molecular motion and no molecular motion without heat. In the second the effect cannot exist without the cause, but the cause may exist without the effect, for the sun shines on the moon but nothing grows there. In the third the cause cannot exist without the effect, for starvation must produce death, but the effect may exist without the cause, since death need not have been produced by starvation. In the fourth case we can have the cause without the effect, and also the effect without the cause; for jealousy may exist without producing crime, and crime may occur without the motive of jealousy. It is plain then that we do not always mean the same thing by our words when we say that two things are related as cause and effect; and anyone who would classify and name the various modes in which two things may be causally related would do a great service to clear thinking.”
In the popular acceptation of the term cause, the same kind of event can have a plurality of (efficient) causes. Death, for example, may be brought about in different cases by different diseases or accidents. But if we understand by the total efficient cause of any given kind of effect the sum-total of agencies and conditions which when present necessitate this kind of an effect, and which are collectively and severally indispensable for its production, then it is obvious that a given kind of effect can have only one kind of such total group of antecedents as total cause, just as any one individual effect can have only one individual total cause, viz. the one which actually produced it; a similar total cause would produce a similar effect, but could not produce the numerically identical individual effect of the other similar cause.[467]
The medieval scholastics discussed the question in connexion with the problem of individuation: “Would Alexander the Great have been the same individual had he been born of other parents than Philip and Olympia?” The question is hardly intelligible. The person born of these other parents might indeed have been as similar as you will to the actual Alexander of history, but would not and could not have been the actual Alexander of history. Nowadays the question discussed in this connexion is not so much whether the same kind of natural phenomenon can be produced by different kinds of total cause—for the answer to this question depends wholly on the wider or the narrower meaning attached to the term “total cause,”[468]—but rather whether or how far the inductive scientist's ideal of searching always for the necessitating and indispensable cause (or, as it is also called, the “reciprocating” or “commensurate” cause) is a practical ideal.