As we have just intimated the principle of causality is frequently employed in the discussion of knowledge in general, and of the knowableness of God in particular. Despite this fact, "the Scholastics did not make the principle of causality an object of special study,"{1} though it is used by them continually. The power the effects have, or the phenomena that begin to be, to teach us about the nature of the something that gave them being is fully recognized and elaborated to great extent by Thomas. And we might say this is the only form under which the question is presented. The idea of cause for Aquinas was acquired as any other idea; it was the result of the abstractive power -- the active intellect -- at work on the deliverance of sense. External reality was not doubted by him; he was aware of immediately perceiving phenomena coming into existence, beginning to be, both internally and externally; and these beginnings must have a something to account for them. Internally, the power of thinking and willing was open to immediate view; change and modification were visible in the world; external objects gave rise to sensation, which in turn led to intellectual operation -- the knowing power is passive, the object is active; all these factors contribute to the idea of cause. The principle was analytic for him, possessing the universality that pertains to every contingent existence stripped of its individual conditions; like all ideas it had its fundamentum in re, and in conjunction with the active intellect received its final form. Thus it was not Hume's observed uniformity of sequence due to custom, nor was it the subjective principle Kant made it out to be. St. Thomas, therefore, could not doubt its validity without running counter to his svstem of Moderate Realism, and the principle of causality, we note from his works, gave him no special alarm.
It is well known that the Scholastics after Aristotle divided all causes into four classes: formal, material, efficient, and final. The formal and material are the constituent principles of a thing, and we get a knowledge of them from the operations and qualities of the thing. And these lead to a knowledge of the final cause or the purpose of the thing. Efficient cause is a principle determing by its action the existence of a contingent thing; it produces something, and thus establishes a nexus or connection between itself and the result of its operation, the effect or thing. Action is its basis -- the cause is the principle or source of action, and the effect is the terminus of the action. Its essential character is production. Though not every cause is efficient, yet every cause looks toward efficiency in some way. We shall consider efficient causality especially, though the arguments that establish its validity are also valid for the other causes.{2} The product or effect of the cause is a manifestation of the nature of the cause and leads to a knowledge of the cause; and it is this point we wish to consider.
This view of causality is based on the principle -- omne agens agit sibi simile -- every agent produces something similar to itself. The action of the cause consists in calling forth in the effect its own form which is a principle of activity -- "for the active power is a principle of acting on something else."{3} From this similarity between the two, we can know something of the cause as shadowed in the effect. Similarity is an agreement in form. The cause is determined to some result either blindly, if a physical cause, or intelligently, if acting from the knowledge of a proposed end. The effect then pre-exists in its cause, and thus every cause produces something like to itself; the closer the resemblance, the more perfect our knowledge of the cause. The effect may adequate or wholly express the power of the cause, or it may be but a far-off hint. "Every effect not equalling the power of the cause receives the likeness of the cause deficiently and not according to the same concept, so that what is divided and manifold in the effects, is simply and in the same way in the cause."{4}
The agreement may be specific, generic, or simply one of proportion, with a lessening knowledge power respectively. The effect is but the manifestation of the power of the cause according the axiom -- operatio sequitur esse. "The effect shows the power of the cause only by reason of the action, which, proceeding from the power, is transmitted to effect. The nature of the cause is known only through the effect in so far as its power, which is in accord with nature, is known."{5} Moreover, "there is the same reason for the effect tending to the likeness of the cause, and for the cause assimilating or rendering the effect like to itself."{6} The effect is contained in the cause in some way, and imitates or resembles the cause in some particular -- and these are the two factors in similarity. "Every effect represents its cause aliqualiter, but diversely: For some effect represents the simple causality of the cause, but not its form, as smoke represents a fire . . . But some effect represents the cause even to the likeness of its form, as produced fire the fire which produces it."{7} Smoke and fire both represent their cause, fire, but not to the same extent; and each in its way gives a knowledge of its cause. There is, however, a distinction between the cause and the effect -- "in every kind of cause, there is always found a distance (difference) between the cause and that of which it is the cause, according to some perfection or power."{8} Mr. Fiske, criticising the phrase we have just been discussing -- the cause is in some way like the effect -- as defended by Mr. Adam in his "Inquiry into the Theories of History," says, "Mr. Adam's reply savors of mediaeval realism."{9} Mr. Fiske seems to demand a total likeness in all cases, which "mediaeval realism" exacted of only certain causes. With the distinctions of St. Thomas regarding the knowledge power of the effect, on the basis of likeness to the cause, the position of Mr. Fiske has no weight.
The knowledge power of the effect depends on what sort of expression the cause has given of itself. Thus the Scholastics spoke of a univocal and an analogical cause. In general, the result of the operation of a univocal cause is a likeness in species between the cause and the effect, as that between a father and his son -- here the effect equals the power of the cause. In the analogical cause, the likeness is not one of quality, but one of proportional relation between cause and effect. In a univocal concept there is an agreement in word and in idea, and everything this idea expresses must apply equally and by the same right to all the objects of which it is affirmed. "Every effect of a univocal cause adequates the power of the cause,"{10} and hence gives the most perfect knowledge of the cause that we can attain to. We do not mention equivocal cause, since "where there is pure equivocation there is no likeness in things, but only a unity of name,"{11} and hence it is not a source of knowledge. Truth is the proportion between concepts and things, as already noted. The analogical concept is not the full manifestation of the cause as the univocal, nor is it a mere metaphor as the equivocal, but it is between them and gives a real, though proportional, knowledge of the cause. It is not equivalent to a metaphor as Caldecott quotes St. Thomas as holding, when speaking of the applicability of certain attributes to God -- "such as are predicable of Him only after the way of analogy or metaphor."{12} Aquinas recognizes both analogy and metaphor, but with a great distinction, as we shall see later on. There is real knowledge in analogical predication. The proportion or relation in analogy may be based on the comparison of two objects to an independent third, or one of the two may be related to the other. This latter is the one of cause and effect, and presupposes that they have something in common in a way, however slight that may be, and thus we are led to a proportional knowledge of the cause by a consideration of the relation of the effect to the cause.
St. Thomas has summarized briefly the three ways an effect can lead us to a knowledge of a cause. "One way, when the effect is taken as a medium for knowing the existence and the nature of the cause, as takes place in the sciences which demonstrate the cause through the effect. Another way, when the cause is seen in the effect itself in so far as the likeness of the cause results in the effect, as man is seen in a mirror on account of his likeness . . . The third way, when the likess of the cause in the effect is the form by which its effect knows the cause . . . But by none of these ways by effect can the cause be known, unless the effect be adequate to the cause, in which the whole power of the cause is expressed."{13} St. Thomas here refers to a complete knowledge of the nature of the cause, not a partial one. An adequate concept gives a knowledge of a thing as it is in itself in as far as it is knowable -- "a thing is known in itself when it is known through a specific likeness adequate to the knowable itself." We can have some knowledge of a thing without having an adequate knowledge of it, and this partial knowledge is given us by all effects. "From every manifest effect we can demonstrate the existence of the cause."{14} The producing power of secondary agents must be admitted, says Aquinas, "or else the nature of no created thing could be known through the effect, and all knowledge of natural science, which relies especially on demonstration through effects, would be taken away.{15}
The degrees of knowledge derived from the effect vary. "The perfection of the effect determines the perfection of the cause."{16} The effect, however, as just noted, is seldom of such a character as to adequate the nature of the cause, hence we need many effects to make our knowledge more stable. Every actual effect "can be infallibly submitted to certain knowledge." "But when we know a contingent effect in its cause only, we have but a conjectural knowledge of it."{17} The larger the number of manifestations and the greater, the more perfect will be our knowledge of the cause. "It is manifest that the causality of a cause and its power is known in proportion to the number and greatness of its known effects."{18} This is important in determining our knowledge of God, for all creation is His work, it contains innumerable manifestations of His Power, and the more we know of them and the more deeply we enter into them, the more complete will be our idea of the Supreme Cause in whom all these effects find a single, harmonious setting.
{1} Kleutgen, La Philosophie Scolastique, v. 2, p. 46.
{2} The Scholastics did not limit causality to efficient causality, as is done in Modern Philosophy, but they considered it in all its aspects, and regarded final as the most important.
{3} Ratio autem activi principii convenit potentiae activae. Nam potentia activa est principium agendi in aliud. Sum. Theol., I, q. 25, a. 1.
{4} Omnis effectus non adaequans virtutem causae agentis, recipit similitudinem agentis non secundum eamdem rationem, sed delicienter: ita ut quod divisim et multipliciter est in effectibus, in causa sit simpliciter et eodem modo. Sum. Theol., I, q. 13, a. 5.
{5} Non effectus ostendit virtutem causae nisi ratione actionis, quae a virtute procedens ad effectum terminatur. Natura autem causae non cognoscitur per effectum nisi in quantum per ipsum cognoscitur virtus ejus, quae natura consequitur. C.G., 1. 3, c. 21.
{6} Ejusdem rationis est quod effectus tendit in similitudinem agentis, et quod agens assimilet sibi effectum. C.G., 1. 3, c. 21.
{7} Omnis effectus aliqualiter repraesentat suam causam, sed diversimode. Nam aliquis effectus repraesentat solam causalitatem causae, non autem formam ejus; sicut fumus repraesentat ignem . . . Aliquis autem effectus repraesentat causam quantum ad similitudinem formae ejus; sicut ignis generatus ignem generantem. Sum. Theol., I, q. 45, a. 7.
{8} In omnibus enim causae generibus semper invenitur distantia inter causam et id cujus est causa, secundum aliquam perfectionem, aut virtutem. Sum. Theol., I, q. 31, a. 1 ad 1.
{9} Outlines of Cosmic Philosophy, v. 2, p. 387.
{10} Omnis effectus agentis univoci adaequat virtutem agentis. Pot., q. 7, a. 7.
{11} Ubi est pura aequivocatio nulla similitudo in rebus attenditur, sed solum unitas nominis. C.G., 1. 1, c. 33.
{12} Selections from the Literature of Theism, p. 19.
{13} Contingit enim ex effectu cognoscere causam multipliciter. Uno modo, secundum quod effectus sumitur ut medium ad cognoscendum de causa quod sit, et quod talis sit, sicut accidit in scientiis quae causam demonstrant per effectum. Alio modo, ita quod in ipso effectu videatur causa in quantum similitudo causae resultat in effectu: sicut homo videtur in speculo propter suam similitudinem . . . Tertio modo, ita quod ista similitudo causae in effectu sit forma qua cognoscit causam suus effectus . . . Nullo autem istorum modorum per effectum potest cognosci causa quid sit, nisi effectus causae adaequatus, in quo tota virtus causae exprimatur. C.G., l. 3, c. 49.
{14} Ex quocumque effectu manifesto nobis potest demonstrari causam esse. Sum Theol., I, q. 2, a. 2 ad 3.
{15} Si igitur res creatae non habent actiones ad producendum effectus, sequitur quod nunquam natura alicujus rei creatae potent cognosci per effectum, et sic subtrahitur nobis omnis cognitio scientiae naturalis, in qua praecipue demonstrationes per effectum sumuntur. C.G., l. 3, c. 69.
{16} Perfectio effectus determinat perfectionem causae. C.G., l. 3, c. 69.
{17} Sum. Theol., I, q. 14, a. 13.
{18} Manifestum est quod causalitas alicujus causae et virtus ejus tanto magis cognoscitur, quanto plures et majores ejus effectus innotescunt. C.G., l. 3, c. 49.