CHAPTER TWO
CHAPTER TWO
The World and Metaphysics It would not be true to say that there is one universally-held opinion among contemporary philosophers about the precise relation between philosophy and the particular sciences.
But all recognize that there is a distinction and that the precise nature of this distinction constitutes a problem.
This recognition presupposes, however, the development of the particular sciences. For it is only because they have developed as branches of study distinct from philosophy that the problem of the precise relation between them and philosophy forces itself on our attention. One would not expect, therefore, to find this problem being stated and treated in any very explicit form in the Middle Ages. Research has indeed shown that more attention was given to scientific inquiry in the thirteenth and fourteenth centuries than used to be supposed.
It has also been shown that the medieval physicists were by no means all slavish copiers of Aristotle and of the Islamic scientists. But when all is said it remains true that the sciences were in a rudimentary state of development in the Middle Ages in comparison with the post-Renaissance era. It is therefore useless to look to the writings of Aquinas for any explicit and thorough discussion of the relation between philosophy and sciences which were still in an embryonic condition. But he does say enough to indicate his general line of thought and to suggest what his point of view would be, were he alive today.
A reader of Aquinas' writings would, however, find it difficult to understand his line of thought unless he was aware of certain important points of terminology.
For example, he would go hopelessly astray if he understood the word scientia in Aquinas as meaning what the word 'science' is usually taken to mean today. For Aquinas the word 'science' meant certain knowledge possessed in virtue
AQUINAS of the application of principles which are either self-evident or known as true in the light of a higher science. Dogmatic theology was considered to be the primary science, in the sense of a branch of study with absolutely certain first principles, revealed by God and yielding certain knowledge.
Metaphysics was also a science for him, possessing its own self-evident principles.
It is therefore evident that Aquinas' use of the word 'science' was not the modern use. Whatever one may think about the cognitive value of theology and metaphysics, one would not normally call them
'sciences' today, not at least without explanation of the sense in which one was employing the terms. Again, one cannot legitimately take it that when Aquinas employs terms like 'natural science' and 'physics' he is using these words in the senses which we should normally attribute to them today.
'Natural science' meant for him the body of certain propositions about nature; and 'natural science' or physics was for Aquinas part of philosophy, namely the part of philosophy which treats of things as capable of motion. He could discuss, therefore, the relation between physics and metaphysics.
But the question what is the precise relation between physics and philosophy would not be a natural question for him to ask, since he regarded physics as part of philosophy.
Aquinas does indeed talk about 'special' sciences or 'particular' sciences. But here also there is room for misunderstanding. Mathematics, for example, is said to be a 'special' science, because it has its own principles; but it is none the less classed under the general heading of philosophy.
It is true that Aquinas makes a distinction between physics and, say, medical science in terms of the general Aristotelian distinction between theoretical science, which is pursued primarily for the sake of knowledge, and practical science, which is pursued primarily for a practical purpose. Thus medical science, though it possesses, of course, a theoretical aspect, is developed for a practical purpose. And it is therefore declared by Aquinas (cf. In Boethium de Trinitate, 5,
1, ad £) not to be a part of physics, which is a speculative or
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theoretical science. Medical science is indirectly related to physics inasmuch as it presupposes a knowledge of the properties of natural things, but it does not fall directly under physics as part of physics. But we are not thereby entitled to regard this distinction between physics and medicine as a distinction between philosophy and science in our sense of the terms. For though 'physics' included for Aquinas much that would later be called cosmology or philosophy of nature or philosophy of science, it also included much that we would regard as belonging to science.
It included, for instance, the general principles of astronomy.
Given this use of terms and the outlook which it implies, the problem, as we understand it, of the relation between philosophy and the sciences can hardly arise. For it to arise it was first necessary that the particular sciences should develop to such an extent as to compel the recognition of their distinction from philosophy. But if we prescind from the terminology and read Aquinas carefully, we can find more than a hint of a distinction between the philosophical propositions which he regarded as certain and empirical hypotheses which are only probable.
He remarks, for example, that the Ptolemaic theory of epicycles may 'save the appearances' but that this is not sufficient proof that the theory is true, 'for the appearances might perhaps also be saved on another hypothesis'
(ST., la, 32, 1, ad 2). Thus although the astronomer may presuppose some very general principles about motion which are regarded by Aquinas as belonging to natural philosophy or physics, it does not follow that the hypotheses which he offers to explain the actual phenomena can be deduced from these general and certain principles. What the astronomer does is to offer a hypothesis which, even if it does in fact account for the phenomena in question (in the sense that if the hypothesis were true, the phenomena would follow), is not thereby proved to be true, since the phenomena might be explained as well or better on another hypothesis.
It has been said by some writers that Aquinas regarded Aristotle's astronomical hypotheses as philosophically true.
AQUINAS And they have interpreted his statement that the Ptolemaic theory is a hypothesis which may be superseded as an expression of his hope that a hypothesis might some day be produced which would account for the phenomena and yet not contradict Aristotle. But there seems to be no adequate reason for attributing to Aquinas this exceptional preference for Aristotle's hypotheses. In his commentary on Aristotle's
De caelo et mundo (2, c.
12, lectio 17) he remarks that though a hypothesis offered in explanation of the movements of the planets seems to explain the facts it does not necessarily follow that the explanation is true, 'for the facts might be explained in another way as yet unknown to men*.
And he is speaking here of Aristotle's theory of homocentric spheres. Hence he seems to put Aristotle's theory of homocentric spheres and the Ptolemaic theory of epicycles and excentrics on exactly the same level. They are both empirical hypotheses which are subject to revision. We cannot, therefore, legitimately attribute to Aquinas the view that contemporary science was irreformable or that it enjoyed the certainty attaching to what he regarded as certainly true propositions of natural philosophy. We cannot deduce from any general definition of motion, for example, the physical explanations of particular motions or sets of motions; and the explanations which are offered are hypothetical in character and not irreformable.
Although therefore we cannot find in Aquinas a clear-cut distinction between philosophy and science in a later sense of the word 'science', we can certainly say that the germ of such a distinction is implicitly contained in the distinction which he draws between philosophical propositions and the empirical hypotheses of contemporary physics and astronomy. And it is clear that if he were alive today he would have no difficulty in recognizing the distinction between philosophy and the particular sciences. And this shows us that we have to beware of taking too seriously the examples which he sometimes borrows from contemporary science to illustrate metaphysical arguments. They are illustrations in terms of ideas familiar to himself and to other thinkers of
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the time; but they are illustrations and not proofs, and we should not attach too much weight to them or imagine that his metaphysics rested simply on contemporary science in our sense of the word 'science'.
We can, however, ask whether Aquinas supposed that the philosopher should first have studied what we would call science.
Logic being presupposed, the order, he says, in which the branches of theoretical philosophy should be studied is this : mathematics, physics, metaphysics. A knowledge of mathematics is required, for example, in astronomy.
We cannot study the heavenly bodies 'without astronomy, for which the whole of mathematics is pre-required'
(In Boethium de Trinitate, c, i, ad 9). And because of its formal character mathematics is best studied before physics, which demands empirical knowledge and a greater maturity of judgement.
Finally comes metaphysics, 'that is, transphysics, which is so called because it is to be learned by us after physics'
(ibid., in corpore). This does not mean that Aquinas thought that the conclusions of 'physics', which included for him, as for Aristotle, psychology, can be derived from mathematical premisses or that metaphysics is dependent on particular astronomical hypotheses.
That physics or natural philosophy should be studied before metaphysics follows from his general principle that the material for reflection is provided by the senses. It is natural to start with what is nearer to us from the cognitive point of view and to consider the physical world as consisting of mobile things before considering things precisely as beings in a science, metaphysics, which culminates in the knowledge of what is most removed from sense-perception, namely God. Metaphysics has its own principles which are of wider application than those of physics, but it is natural for us to come to a knowledge of the more general and abstract through a knowledge of the less general and abstract. And this point of view may well suggest that Aquinas expected of the philosopher a knowledge of the science of his time.
He certainly did not demand of the student of philosophy a knowledge of all the sciences which he recognized as such.
AQUINAS He did not expect the metaphysician to have studied, for example, medical science. And when he said that physics should be studied before metaphysics he was doubtless thinking primarily of the general principles and concepts of natural philosophy. At the same time he obviously thought of the natural philosopher as acquainting himself with the relevant empirical data. Without some knowledge of the empirical data the psychologist, for example, could not discuss in an intelligent manner the relation between soul and body. This is simply a matter of common sense. But it would be extremely rash to make the dogmatic and unverifiable statement that because Aquinas said that 'physics' should be studied before metaphysics he would therefore say, were he alive now, that the metaphysician should first have studied science, if we mean by this that he should be a specialist in some particular science. After all, it is a life's work to become a specialist in any science. And the demand for a universal knowledge of science would be simply fantastic.
He would doubtless say that if we wish to philosophize about science or about the relation of soul to body, we must have a good knowledge of the relevant empirical data. This would be demanded not only by common sense but also by Aquinas' general conceptions of the way in which we acquire knowledge. But if we consider his idea of metaphysics, to which I shall turn presently, we can hardly avoid the conclusion that he would be particularly concerned with vindicating the independence of metaphysics from the empirical hypotheses of the sciences. For example, he would doubtless point out that the advance of science in no way alters the facts on which he bases his arguments for the existence of God. Whether we think of things in terms of the four elements or whether we think of them in terms of the atomic and electronic hypotheses makes no difference to the fact that there are things which change or to the fact that there are things which come into being and pass away.
If the existence of finite things implies the existence of infinite being, the relation of existential dependence of the former on the latter is unaffected by the varying stages of 7*
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our scientific knowledge about finite things. Of course, the retort might be made that if Aquinas were alive today he would change his conception of metaphysics. But if in asking what Aquinas would hold today about the relation between metaphysics and science one intends to ask a sensible question and not to give free play to the construction of unverifiable hypotheses, the question must, I think, be equivalent to asking what view of the relation between metaphysics and science, in the modern use of this word, would be demanded by the idea which he actually had of metaphysics. And the answer can hardly be anything else but that he would have to emphasize rather than minimize the distinction between metaphysics and science. The view that metaphysical theories are nothing but themselves empirical hypotheses, depending on the empirical hypotheses of the sciences, is a possible view of metaphysics, but it was not that of Aquinas.
There is one further point which can be alluded to briefly.
The fact that many themes which we would classify as belonging to science were classified by Aquinas under the general heading of 'philosophy' gives rise to the question whether the whole content of what he called 'physics' has been absorbed in what we would call 'science'. Does there remain any room at all for 'natural philosophy' ?
Possibly an answer can be suggested on these lines. In his discussions of motion, time, and space, which are to be found principally in the commentaries on Aristotle, Aquinas accepted the latter's definitions. In the Summa theologica we read that 'since in any sort of motion there is succession, and one part after another, by the very fact that we number before and after in motion we apprehend time, which is nothing else but the number of before and after in motion' (S.T., la, 10, i).
But whatever we may think of the Aristotelian definitions the point is that in discussing time, space, and motion Aquinas did not think that he was discussing subsistent things. Space, for example, is not a thing. Hence it is reasonable to say that he was engaged in analysing or clarifying the concepts of time, space, and motion or the meanings of these terms. And
AQUINAS if we are prepared to call this sort of analysis 'philosophical', we can say that it is not the whole content of what Aquinas called 'physics' and classed under the general heading of 'philosophy' that has been absorbed in what we call 'science'.
The different particular sciences are concerned, Aquinas would say, either with different kinds of beings or with the same things considered under different aspects and from different points of view. Astronomy and psychology, for example, though they may both belong to 'natural philosophy', do not treat of the same objects. Both the anatomist and the psychologist, however, are concerned with the human being. But they do not consider the human being from the same point of view, and their sciences are different, even though there may be points of connexion between them. Again, biology is concerned with organic being or with corporeal living being. Certainly, a more natural way of expressing this might be to say that the biologist studies living bodies or that he studies the life of animals and plants.
But though he obviously has to study individual specimens he is not concerned with definite individual organisms in the way in which an amateur gardener is concerned with the individual flowers and shrubs which he plants and tends.
The biologist is concerned with type and species rather than with the individual as such. We can therefore say that he is concerned with organic being or with being considered precisely as organic, provided that we do not take this to imply that there is a subsistent organic being separate from concrete individual organisms.
It is possible, however, to abstract from differences like organic and inorganic and to consider things simply as beings. And Aquinas follows Aristotle in defining metaphysics as the science of being as being. But it would be a great mistake to interpret this as meaning that there is something called 'being', apart from individual beings or things.
Aquinas certainly speaks of God as Being; but when he says that metaphysics is the science of being as being, he is not
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making it synonymous with what is called 'natural theology'. He means, in part at least, that metaphysics is concerned with the analysis of what exists or can exist, considered as such. And that of which we say primarily that it exists or can exist is, according to him, substance (a concept to which I shall return presently).
If we say that Peter exists we assert that a definite substance or thing exists.
If we assert that Peter is white, we predicate a quality of Peter.
We say that it exists, but as a quality of Peter and not in its own right, so to speak. And if we assert that whiteness exists as a quality of Peter, we assert by implication that Peter exists. For it would be absurd to say both that Peter does not exist and that he is white. It is therefore substances of which we primarily affirm existence. Accordingly, if 'being' is taken in the sense of that which exists or can exist, metaphysics is primarily concerned with the analysis of substance and its modifications. Thus it is an analysis of the fundamental categories of being; of substance, that is to say, and of the various types of accident, such as quality and relation.
Metaphysics is also, for Aquinas as for Aristotle, an analysis of the causes of substance.
It includes, for example, an analysis of efficient causality. In the course of ordinary life we often ask for or look for the particular cause of a particular event. We ask, for example, what caused the door to bang, and we receive the answer perhaps that the banging of the door was caused by a gust of wind coming in through a window which had just been opened. But it is also possible to inquire into the nature of efficient causality as such, in abstraction from this or that particular efficient cause or particular type of efficient cause. So, too, it is possible to inquire into the nature of final causality. Thus the metaphysician concerns himself with the analysis of the different kinds of causality as well as of the categories of substance and accident.
Now, if this aspect of metaphysics is taken to be the whole of metaphysics, it is obvious that the activity of the metaphysician is one of analysis.
The metaphysician's business would be to clarify the concepts of causality, of
AQUINAS substance, of relation, and so on. Indeed, we could say that he is concerned with analysing the meanings of certain terms, provided, of course, that we allowed for the fact that he seeks to exhibit the real or true meanings of the terms in the light of experiential data and is not acting as a grammarian. Some may prefer to say that he is concerned with 'essences'; but we can just as well say that he is concerned with 'meanings'. There is, for example, no causalityin-itself subsisting apart from particular causal relations; nor did Aquinas ever think that there is. When, therefore, the metaphysician analyses causality, we can legitimately say that he is analysing the meaning of the term 'causality', provided that this is understood as implying that he is concerned with exhibiting what people ought to mean by the term and not with saying simply what Smith or Brown imagines that it means or may mean.
This aspect of metaphysics is a real aspect of it as conceived by Aquinas; but it is certainly not the only aspect.
The word 'being' can be understood in the verbal sense of 'to be' or 'to exist' (esse). And then to say that metaphysics is concerned with being is to say that it is concerned with existence. And existence here means the concrete act of existing. Looked at under this aspect metaphysics is concerned above all, for Aquinas, with accounting for or explaining the existence of things which change and which come into being and pass away. As we have seen earlier, Aquinas asserts that the whole of metaphysics is directed towards the knowledge of God. And since God lies beyond our natural experience and we can know Him only in so far as we can understand the relation of the objects of experience to the ground of their existence, an assertion of the theocentric character of metaphysics necessarily implies that it centres round the analysis of the existential dependence of finite existence.
The two aspects of metaphysics cannot, indeed, be dissociated from one another. But if we like to call the first aspect the 'essentialist' aspect and the second the 'existentialist' aspect, as some writers like to do, we can say that it
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is in emphasizing the existentialist aspect that Aquinas goes beyond Aristotle. For the latter did not raise the problem of the existence of finite things; and this means, of course, that he did not see that there is any problem. And he did not see that there is any problem because he concentrated on what a thing is, on the ways in which something is or can be, and not on the act of existing itself. Aquinas, however, while retaining the Aristotelian analyses of substance and accident, form and matter, act and potency, placed the emphasis in his metaphysics, not on 'essence', on what a thing is, but on existence, considered as the act of existing. This notion of the act of existing is indeed very difficult, and I shall return to it; but it is worth while pointing out here that this change of emphasis had its repercussions on the metaphysical analyses which Aquinas inherited from Aristotle.
For example, though for Aristotle substances exist, in the sense that there are substances, he is concerned as a metaphysician with the analysis of concepts, with the concepts, in this case, of substance and accident, and he says nothing about the existential dependence of finite substances. The world is a world of substances or things, but the world is eternal and uncreated, and it is against the background of this eternal and uncreated world that Aristotle analyses the concept of substance. Aquinas took over the Aristotelian analysis of substance, but at the same time the world for him consisted of finite substances, each of which is totally dependent on God.
It is true that this does not intrinsically alter the analysis of the nature of substance; but it sets substances in a new light. And it sets them in a new light because emphasis is placed on the act by which substances exist, an act of existing received from an external cause.
Thus in general, while it is perfectly true that Aquinas took over the Aristotelian metaphysical analyses of substance and accident, act and potency, causality and so on, it is also true that his concentration on being considered as existence (as esse) set in a new light the world which Aristotle described in his metaphysics.
AQUINAS We may talk about a tree as a thing, but we would hardly describe the colour of its leaves as a thing. And if we examine ordinary language we find many instances of a distinction being made or implied between a thing and its attributes or between a thing and the relations in which it stands to other things. We may say at one time, for example, that John is pale and at another time that he is sunburnt, or at one time that he is well and at another time that he is ill.
We say of a traveller that he is in one city on Monday, in another city on Tuesday. We all make statements in which we successively attribute to ourselves different states. The ordinary man does not indeed reflect on this fact about the language he uses; but the statements which he makes imply a recognition in practice of a distinction between things and their modifications, between 'substance' and accidents, between that of which we predicate qualities, quantity, and relations and qualities and relations which exist only as qualities and relations of that of which they are predicated.
We can say that Peter is sitting on a chair, but nobody would expect to encounter the relation of 'sitting on' existing as an entity apart from any sitter.
There cannot be any doubt, therefore, that the ordinary man makes a distinction between things and their modifications. We have only to examine what we are accustomed to say about the changing size of a tree or the changing colour of its leaves to see that this is the case. Nor can there be any doubt that the ordinary man would regard this linguistic distinction as objectively justified. And it is this spontaneous conviction of the ordinary man which lies at the basis of the substance-accident metaphysic.
For the philosopher like Aquinas who accepts this metaphysic, ordinary language reflects the common experience of men, and in common experience a distinction between substance and accident is implicitly recognized. What the philosopher does is not to invent a gratuitous theory or even to make a discovery of which the ordinary man has no inkling, but rather to express explicitly and in abstract terms a distinction which is implicitly recognized by the ordinary man in
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concrete instances. A substance is that of which we say primarily that it exists and which is not predicated of something else in the way in which we predicate pallor of John or redness of a rose, while an accident is that which exists only as a modification of a substance or thing and which is predicated of a substance. The theory of substance and accidents as maintained by Aquinas has, of course, several refinements.
It is necessary, for example, to distinguish between accidents like quantity and quality on the one hand and relations on the other. But so long as the theory is expressed in a very general way, with reference to the distinctions which we make in ordinary language between things and their modifications, it can be grasped by practically anyone. The difficulties begin at the point when exact analysis is undertaken.
These difficulties are only increased if the theory is taken to mean that there is an unknowable substratum called 'substance' which serves to hold together a collection of phenomena or accidents. This may represent the theory of Locke, but it does not represent the theory of Aquinas. For the latter the distinction between substance and accident is a distinction not between an unknowable substratum and knowable modifications but between that which exists, if it does exist, as subject and that which exists only as a modification of a subject. In Aquinas' own terminology the word
'substance' signifies 'an essence to which it pertains to exist by itself (per se; S.T., la, 3, 5, ad 1). This phrase per se has to be carefully understood. It does not mean that a substance exists 'by itself in the sense that it has no cause
: it has to be taken in opposition to existing by another, that is, as a modification of something else. A substance does not exist per se in the sense in which God can be said to exist per se. Indeed,
God does not fall under the category of substance, and He can be called 'substance' only in an analogical sense. A human being, for example, does not exist per se, if by this we mean that he or she has no cause and is completely independent. But at the same time a human being does not exist as the modification of another thing, in the sense in
AQUINAS which John's anger has no existence apart from John. And in this sense a human being exists per se. But this is not to say that John's substance is an unknowable substratum hidden away under John's accidents : it is not an unknowable and completely unchanging X, entirely inaccessible to the human mind. In knowing John's accidents or modifications we know John's substance in so far as it reveals itself in and through these modifications. Considered in itself a substance is not a phenomenon, that is to say, apart from its modifications it is not the direct object either of any sense or of introspection. When I look at a tree, I do not and cannot see the substance of the tree apart from the tree's colours and so on. But inasmuch as the colours of the tree manifest the substance, I can properly be said to perceive the substance. What I perceive is neither an unattached accident or set of accidents nor an unmodified substance
I perceive a modified thing. Similarly, through introspection I can perceive desires, emotions, and thoughts, but in perceiving them
I perceive the substance. We can say that the accidents of a thing change. The colour of the leaves of many trees changes, and the size of a human being changes as he or she grows up. But strictly speaking, it is the substance which changes; it changes 'accidentally'. That is to say, a human being, for example, changes in many ways during the course of his or her life, while it remains the same definite human being. The changes do not take place round an unchanging core called 'substance'
: it is the latter itself which changes. Hence in knowing the changing states or modifications or accidents we know, to that extent at least, the substance itself. Aquinas does indeed say that the name 'substance' is derived from standing under (nomen enim substantiae imponitur a substando; In I Sent., 8, 4, 2) and that substance is that whose act is to stand under (substantia (dicitur) cuius actus est substare; In I Sent., 23, 1, 1). And we see here how the use of the word substantia tends to emphasize an aspect of substance which is not so emphasized by the use of the Greek word ousia. But all the same Aquinas is not talking about an unchanging and un-
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knowable substratum but about a subject which is not itself a determination of another thing but which has determinations or modifications through which it is known.
It is true that according to Aquinas we do not ordinarily have direct intuitions of the essences or substances of things. He says, for example, that 'substantial differences, because they are unknown, are manifested by accidental differences'
(In De generatione et corruptione, I, c.
3, lectio 8). But the last words of this quotation show the impropriety of ascribing to him the doctrine that there is an unknowable substrate called 'substance'. As we have seen, Aquinas did not admit that we have a direct intuition of our souls, but he did not mean that they are unknowable ghosts hidden away in our
1 They are knowable in and through their activities.
The point can be expressed in this way. Considered as a bodies. centre of activity, substance is called by Aquinas 'nature', just as it is called 'essence' when considered as definable.
And one of his principles was that activity or operation 'follows', and so manifests, being : operatio sequitur esse.
Hence we can say that for him we distinguish different substances as different individual centres of characteristic activity. And in knowing these activities we know the substances from which they proceed.
I come to know anothef person by listening to his words and observing his actions; for his words and activities reveal him in different ways.
The connexion between the substance-accident metaphysic and ordinary language has been noted above. But it should also be mentioned that this metaphysical theory is not infrequently interpreted as being no more than a reflection of the linguistic distinction between subject and predicate or a projection into reality of the subject-predicate form of proposition. In other words, it is maintained that the theory was the result of linguistic practice.
If Aristotle had spoken a language in which this form of proposition did not occur, he would not have developed the substance1.
I do not mean to imply that for Aquinas the soul is the whole essence or substance of the human being. Peter is a unity of soul and body, not a soul in a body.
AQUINAS 1 The fact that he did develop it shows that accident theory. he was misled by language. And medieval Scholastics who proposed this theory were misled in the same way.
Aquinas would doubtless regard this interpretation of the substance-accident theory as an instance of putting the cart before the horse. We are aware in experience of our own changing states as ours and of the changing states and activities of other things as belonging to those things. And it is this experience which lies at the basis of the substance-accident metaphysic rather than a mistaken conviction that the structure of reality must correspond to the structure of language.
Aquinas could point out that a distinction between a thing and its states or modifications can be made and is made even in languages in which the subject-copula-predicate form of proposition is not normally used.
It may be urged, of course, that though Semitic languages like Hebrew and Arabic can give expression without the normal use of the copula to the fact that a person or a thing is in this or that state or possesses this or that quality, the substance-accident metaphysic was actually developed by a philosopher, Aristotle, who spoke a language in which this form of proposition is used, and that the medieval philosophers who adopted this metaphysic also used languages in which the same form appears. This can, indeed, hardly be said of the medieval Islamic philosophers.
Avicenna, for example, generally wrote in Arabic.
It might perhaps be maintained that the Islamic Aristotelians adopted the substance-accident theory simply because it was Aristotle's.
But they also thought that it was true.
If Aquinas were alive today he would certainly be compelled to meet objections against the substance-accident metaphysic which were not raised in his own time, when this theory was common property. But as far as the purely linguistic interpretation is concerned I think that he would argue on the lines indicated above, i.
It is sometimes said that Aristotle had no doctrine of substance, and that ousia should not be translated as substance. This is true if by 'substance' is meant Locke's unknowable substratum. But Locke's theory was held neither by Aristotle nor by Aquinas.
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trying at the same time to avoid falling into Locke's theory of. an unknowable substratum.
The world therefore consists of a multiplicity of substances: it is not itself a substance. There is a multiplicity of individual things which stand in different relations to one another and each of which undergoes accidental changes, that is, changes which do not alter the specific character of the substance. A man undergoes many changes while remaining a man. But it is possible to pursue further the analysis of material things. An oak tree grows, and the colour of its leaves changes, but we still speak of it as though it were the same oak tree. But if the tree is burned and reduced to ashes, we do not speak of the ashes as an oak tree. When bread has been digested we no longer speak of it as bread. Yet neither in the case of the oak tree which has been reduced to ashes nor in the case of the bread which has been digested is the matter of the oak tree or of the bread annihilated. There is permanence, and yet at the same time there is a change which is more than 'accidental'. And the combination of these two factors gave rise to a problem for Aquinas as for Aristotle. What does change of this kind, substantial change, imply with regard to material things?
It implies, Aquinas answered, that in every material thing or substance there are two distinguishable constitutive prin1 One of these he called 'substantial form'. In the case ciples. of an oak tree, for example, the substantial form, corresponding to Aristotle's 'entelechy', is the determining principle which makes the oak tree what it is. This form must not, of course, be confused with the outward shape or figure of the tree: it is an immanent constitutive principle of i. The word 'element' might suggest chemical element and so be misleading. By calling matter and form 'principles', Aquinas means that they are the primary co-constituents of a material thing. The word is obviously not being used in the sense of a logical principle; nor does it refer to observable chemical elements. Matter and form are 'principles of being' (principia entis); they are not themselves physical entities.
AQUINAS activity which makes the oak tree an oak tree, stamping it, as it were, as this particular kind of organism and determining it to act as a totality in certain specified ways. But what is it that the substantial form of the oak tree 'informs' or determines? We might be inclined to answer that it is the matter of the tree, meaning by this the visible material which can be chemically analysed. But ultimately, Aquinas thought, we must arrive at the concept of a purely indeterminate potential element which has no definite form of its own and no definite characteristics. This he called 'first matter' (materia prima). Visible matter, secondary matter, is already informed and possesses determinate characteristics; but if we think away all forms and all determinate characteristics we arrive at the notion of a purely indeterminate constitutive principle which is capable of existing successively in union with an indefinite multiplicity of forms. When the oak tree perishes, its substantial form disappears, relapsing into the potentiality of matter, but the first matter of the tree does not disappear.
It does not, and indeed cannot, exist by itself; for any existent material substance is something definite and determinate. When the oak tree perishes, the matter immediately exists under another form or forms. When a human being dies and his body disintegrates, the matter is at once informed by other forms. But there is continuity, and it is first matter which is the element of continuity.
According to Aquinas, therefore, every material thing or substance is composed of a substantial form and first matter.
Neither principle is itself a thing or substance; the two together are the component principles of a substance. And it is only of the substance that we can properly say that it exists. 'Matter cannot be said to be; it is the substance itself which exists' (C.G., 2, 54).
1 was not new. Derived from Aristotle it was common property in the Middle Ages,
This theory of matter and form 1.
It is commonly known as the 'hylomorphic' theory, this name being derived from the combination of the Greek words
%hr\ and
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though different thinkers propounded it in different ways.
But I do not want to discuss its origins or the different versions of it : for our present purpose it is more appropriate to note the following points. In the first place there is at least some connexion between the theory and ordinary experience and language. We are accustomed to speak of one thing becoming another thing or of one kind of thing becoming another kind of thing. And this way of speaking seems to imply that change involves both continuity and discontinuity.
There is continuity because that which changes is not annihilated, and there is discontinuity because there is first one kind of thing and then another kind of thing. In the second place, however, the theory seems to be clearly a metaphysical theory.
First matter is not, and cannot be, the direct object of experience : it is postulated as the result of an analysis of experience. And this analysis is obviously not physical or chemical analysis. Aquinas knew nothing, of course, of modern chemistry or of the atomicelectronic hypothesis; but he regarded the hylomorphic theory as being independent of contemporary ideas about, for example, physical elements like fire and water. For him it was the result of metaphysical analysis, not of physical or chemical analysis. The language of the theory of form and matter belongs to the language of metaphysics.
This does not mean that for Aquinas form and matter are occult entities in the sense that nothing at all can be known about them. True, first matter does not and cannot exist by itself; it cannot as such be seen; but its presence as a component metaphysical factor in corporeal substances is manifested by substantial change. Again, we may not be able to know the form of a given corporeal substance to the extent of being able to define it in terms of genus and specific difference : in practice we may have to be content with a definition in terms of properties. But the form is the principle or source of the characteristic qualities, activity and behaviour of a substance, and it is known to the extent in which it is manifested in these qualities and activities. For example, the presence and nature of a vital form in an organ9i
AQUINAS ism is revealed through the characteristic activities of the organism.
There is a further point to be noted.
If the theory of matter and form is interpreted as a metaphysical theory and as being independent of the results of empirical scientific research, it follows that no new empirically verifiable scientific propositions can be derived from it. One could certainly deduce from the theory the conclusion that changes of a certain type are possible. But observation of these changes is one of the main grounds for asserting the theory in the first place. The statement therefore that such changes are possible would not be a new empirically verifiable proposition. Hence the theory cannot be used as an instrument in the progress of natural science. And those Aristotelians of a later date, namely of the time of the Renaissance, who talked as though the theory had a place in natural science misconceived its nature. For the purposes of natural science the theory is 'useless', if by a theory's being 'useful' in natural science one means that new empirically verifiable, or rather testable, propositions can be derived from it.
It does not follow, however, that the theory may not have proved useful to science in another sense. For the theory of forms presents us with a world which is not simply and solely a Heraclitean flux but a world shot through, as it were, with intelligibility. Through reflection on the activity and behaviour of things we can come to some knowledge at least of their intelligible structure. And it is arguable that this picture of the world as intelligible and of material substances as proportionate to the human mind and as relatively transparent in their formal structure acted as a preparatory condition for, and stimulus to, empirical scientific research.
This consideration gives rise in turn to the question whether the metaphysical theory of form and matter, in its application to inorganic substances at least, has not been rendered otiose by scientific research, in the sense that scientific research gives body and concrete shape to the vague idea of form presented in the metaphysical theory. This
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question is connected with the general question of the relation between scientific hypotheses and metaphysical theories about visible things; and this general question is too far-reaching to discuss here. But it is worth while mentioning it at any rate. As regards the particular question about the relation of the hylomorphic theory to scientific theories of atomic and electronic structure it should be noted that those followers of Aquinas who maintain the truth of the theory, even in its application to the inorganic world, insist on its metaphysical character and on its independence of the changing hypotheses of science. Form and matter are the metaphysical constitutive elements of bodies, in the sense that reflective analysis of bodies or of corporeal substance as such, rather than as this or that kind of corporeal substance, reveals their presence. The theory may be
'useless' in the sense indicated above; but to say this is simply to say that the theory is not a theory of empirical science. There are, however, other followers of Aquinas who consider that the theory was the result of a speculative attempt to cope with a problem which is solved, so far as it can ever be finally solved, by scientific research.
I do not feel inclined to hazard any opinion as to what Aquinas himself would say on this matter, were he alive today. Questions of this sort obviously cannot be answered in a definitive manner.
It is sufficient to say that Aquinas regarded the theory as being independent of contemporary 'scientific' ideas.
Though corporeal things or substances are alike in that each is composed of form and matter, not all corporeal forms are alike. Dogs and cats are both corporeal things, but they differ specifically from one another; in the language of the formmatter theory the canine form differs specifically from the feline form. The form of salt differs from that of water. We have therefore groups of corporeal things, the members of each group possessing similar substantial forms. The members of a species do not, of course, possess numerically the same substantial form. Aquinas rejected altogether the ultra-
AQUINAS realist theory which supposes that because we can use the same word of a number of individuals there must therefore be one thing corresponding to that word.
It is fallacious to argue that because we say Vetrus est homo (Peter is a man) and Joannes est homo (John is a man) there is therefore one universal entity present in both Peter and John. Universality as such is only 'in the mind' (cf. S.T., la, 85, 2, ad 2). But at the same time Aquinas was convinced that there are real species, and that the members of a species possess similar substantial forms. And it is this objective similarity of form which enables us to have universal specific concepts, and so to apply the same universal term to all the members of a specific class. The members of a class possess similar natures.
And so when the mind forms universal concepts it does not construct a false picture of reality. For that which is conceived, say human nature, exists extra-mentally, though it does not exist outside the mind in the way in which it is conceived, that is, as a universal (cf. ST., la, 85, 1, ad 1).
Ordinary people are, of course, implicitly aware of this; for they use universal terms quite correctly in the concrete propositions of everyday language without ever looking for universal entities corresponding to the terms they use.
It is when philosophical analysis starts that the trouble begins.
And we can say that one of the services of Aquinas and his forerunners in the matter of universals was to expose the falsity of ultra-realism.
Perhaps it might be as well to remark at this point that when Aquinas talks about groups of corporeal things possessing similar 'natures' or 'essences' he does not refer simply to the form. The word essence in regard to composite substances signifies that which is composed of matter and form'
(De ente et essentia, II). The universal idea of man, for instance, abstracts from the individual characteristics of Peter and John, but it does not abstract from the possession of matter. That is to say, the universal idea of 'human being' is the idea of a substance composed of matter and rational soul, which for Aquinas is the form in the case of man; it is not the idea of the soul alone. It is, however, the form which
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determines a substance to be a substance of a particular kind, to fall, that is to say, into a particular class. And so it is the similarity of form in members of a species which is the objective foundation of the universal specific concept.
But this view gives rise to a problem.
If the substantial forms of the members of any given species are radically alike, it follows, argued Aquinas, that the difference between the members cannot be ascribed primarily to the form as such. That which makes two pieces of flint two pieces and not one is not the fact that both are flint; for in this respect they do not differ. To what factor, then, must individuation be primarily ascribed ?
It must be due primarily to matter, not to matter considered as purely indeterminate, but to matter as quantified. In the case of the two pieces of flint their flintness brings them together, as it were, and, considered in itself, does not distinguish them. They are distinguished by the fact that the flintness of the one is present in this matter and the flintness of the other in another matter.
It is matter which is the principle of individuation and which marks off one corporeal thing from other members of the same species.
1 This must not be taken to mean that the form of an oak tree, for example, existed with some kind of universal status before the tree came into existence. As we have seen, there are no extra-mental universal entities. But if one supposes that the oak is composed of form and matter, it makes sense to ask which component element is primarily responsible for the oak being this particular oak. And in Aquinas' opinion it is matter which is primarily responsible.
For the oak-ness of one oak does not differ from that of another save through the fact that it informs different matter.
There are various rather obscure refinements of the theory of matter as the principle of individuation which might be added. But I prefer to omit them and to draw attention to i. Aquinas drew the logical conclusion that in the case of immaterial beings there can be no multiplication within a species.
Each angel is the sole member of its species.
AQUINAS one important application of the theory. The latter was by no means acceptable to all the contemporaries of Aquinas; and one of the reasons why it was attacked was that it seemed to a number of theologians to be incompatible with the Christian view of the soul.
It seemed at least to be derogatory to the dignity of the human soul to say that it is individuated by matter. But Aquinas did not hesitate to grasp the bull by the horns. He certainly maintained, as will be seen in a later chapter, that the human soul is spiritual and that it survives bodily death; but he also held, as we saw in the last chapter, that the mind is originally like a wax tablet on which nothing has been written. What makes human souls different from one another is their union with different bodies. 'For this soul is commensurate with this body and not with that, that soul with that body, and so with all of them' (C.G., 2, 81). And Aquinas draws the logical conclusion.
'It is clear that the better disposed a body is the 1 This is obvious in the better is the soul which falls to its lot.' case of those things which are specifically different. And the reason is that act and form are received in matter according to the capacity of the matter. Therefore since some human beings have better disposed bodies, they possess souls with a greater power of understanding. Hence it is said (by Aristotle in the De anima,
2, 9; 421a, 25-6) that we -see that those with soft flesh are mentally more alert' (S.T., la, 85, 7).
Some of this is rather crude, of course, but it is obvious that Aquinas' theory of matter as the principle of individuation would lead him to welcome, as confirmation of the theory, rather than to fear the results of modern research into the dependence of psychical on physical differences.
The distinction between form and matter was for Aquinas a subdivision of the wider distinction between act and poten1. These words must not be understood as implying that Aquinas thought of human souls as existing before their union with bodies.
He believed that each human soul is created by God but not that it is created previous to the body's formation.
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tiality. First matter, considered in abstraction, is pure potentiality for successive actualization by substantial forms, each of which stands to its matter as act to potentiality, actualizing the matter's potentiality.
But the distinction between matter and form is applicable only to corporeal things, whereas the distinction between act and potentiality is found in all finite things.
The general idea of a distinction between act and potentiality can be illustrated easily enough from ordinary language.
I might say of myself, 'I am writing, but I can go for a walk if you wish.' Or we might say of someone, 'He is perfectly capable of lifting that weight if he chooses to do so.' Or it might be said of a wooden plank, 'Yes, it is a fine plank, but it can be split up into small bits for firewood, if necessary.' Or it might be said of water that it is water but that it can become or be turned into steam.
I am actually writing, but I am capable of or have the potentiality for going for a walk. The man is not actually lifting the heavy weight, but he is capable of doing so; he has the capacity or potentiality for it. The plank is actually a plank, but it is capable of being divided. The water is actually water, but it possesses the power or potentiality of becoming steam. Of course, it might be maintained that the distinctions which I have appealed to in propositions of ordinary language are linguistic distinctions simply, and that all that I have done is to draw attention to distinctions we make when speaking about things. But Aquinas was convinced that the linguistic distinctions exhibit objective distinctions in things. That which can be and is not is said to exist in potency, while that which already is is said to exist in act' (De principiis naturae, in first sentence).
This distinction between act and potentiality is found, according to Aquinas, in every finite thing, though not necessarily in the same way. An oak tree can undergo substantial change, but a spiritual being cannot. Yet an angel has the potentiality of making acts of love of God. Wherever there is finitude, there is, so to speak, a mixture of act and potentiality. No finite being can exist without being actually
AQUINAS something definite, but it never exhausts its potentialities all at once. Development of some sort, further actualization of some sort, is always possible.
Possibility of development is thus a manifestation of finiteness. For example, it makes sense to talk of mental development through the acquisition of knowledge only in the case of a finite intelligent being.
It would be a contradiction to speak of an infinite omniscient mind acquiring knowledge. For knowledge can be acquired only by a mind which does not already possess that knowledge. But it does not follow that a finite mind's capacity for acquiring knowledge is an imperfection in the sense that it is something which it would be better to be without. The human mind, which begins in a state of total ignorance, has a capacity for developing itself by acquiring knowledge; and Aquinas certainly never imagined that it would be better for the human mind if it lacked that capacity and was doomed to remain completely ignorant. The mind's capacity for acquiring knowledge cannot therefore be called an imperfection, though it manifests the mind's finiteness. Thus Aquinas did not deny or belittle a 'dynamic' conception of the universe. On the contrary, he saw in all things. a natural tendency to realize or develop their several potentialities, and he regarded this tendency as something good. There is nothing in the idea of self-development and self-perfection through activity which is incompatible with Aquinas' philosophy. At the same time the capacity of acquiring knowledge, for example, exists for the actual acquisition of knowledge, and the habitual possession of it exists for its exercise. 'The end (that is, purpose) of a potentiality is act' (ST., la, Ilae, 55, 1). 'Each thing is perfect in so far as it is in act, for potentiality without act is imperfect' (ST., la, Ilae, 3, 2). A capacity for self-development is not an imperfection in the sense that it is something which it would better to be without; but it is imperfect when compared with the actual development. Aquinas was not the man to exalt striving at the expense of possession, to say, for example, that it is better to search endlessly for truth than to know what is true or that the striving for
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moral virtue is superior to its possession. Yet the habitual knowledge exists for its exercise, and moral virtues are acquired with a view to moral action.
These points of view come together in Aquinas' hierarchic conception of reality. At the bottom of the scale, so to speak, is 'first matter', which cannot exist by itself because it is sheer potentiality for the successive reception of substantial forms capable of informing matter.
1 At the top of the scale (though this is an inexact way of speaking, since God, as infinite transcendent being, cannot be placed in a common class with finite things) is God, who is pure act without any unrealized potentialities. If therefore we compare the levels of the hierarchy of being, we shall have to say that the possession of potentiality as such - 1 mean unrealized capacity is an imperfection in the sense that it indicates a lack of possible perfection, a need to be fulfilled. Finite beings are less perfect than God. But at the same time any finite being would be less perfect than it actually is, if it lacked all capacity for self-development. The development which we find in the universe is a sign of the finitude of the things which compose it, but any finite being is necessarily a mixture of potentiality and act, and development is a movement towards the full realization of form. A static universe, were such a thing possible, would not be better than a dynamic universe. God is the measure of all things, to quote Plato's retort to Protagoras; but it is only through self-development that finite things can imitate, as it were, the fullness of the divine actuality.
For Aquinas, therefore, the distinction between potentiality and act is found in all finite things. But to say that these factors are found in every finite thing does not by itself tell us very much. A human being, for instance, certainly possesses potentiality or capacity, but we want to know what precise capacities he possesses. However, we are keeping at i. Nor can substantial forms, apart from the human soul, exist by themselves.
AQUINAS present to the most general principles of Aquinas' philosophy and to his assertions about finite things in general rather than about one kind of finite being. We first considered a particular exemplification of the distinction between potentiality and act that is found in all corporeal things, namely the distinction between matter and form, of which the latter stands to the former as act to potentiality.
And we used this particular distinction as an introduction to the more general distinction. We must now consider an example of the potentiality-act relation which is found, according to Aquinas, in all finite things, whether corporeal or incorporeal, namely the relation between essence and existence.
Aquinas' distinction between essence and existence is somewhat difficult to understand.
It is true that a preliminary notion of it can be given in terms of ordinary language.
For in ordinary language we are accustomed to distinguish between the whatness or nature or essence of a thing and the fact that it exists.
If a child comes across the words 'elephant' and 'dinosaur' in a book and does not know what the words mean, the meanings could be explained to him without its being added that there are elephants but no dinosaurs.
In this case the child would have some notion of the whatness of an elephant without knowing that there are things to which the description applies. But though a preliminary idea of Aquinas' distinction between essence and existence can be given in some such way, difficulties arise directly we try to go beyond this preliminary idea (which can itself be misleading).
However, as Aquinas attached a very considerable importance to the distinction it cannot possibly be passed over in a book on his philosophy.
First of all, what does Aquinas mean by 'essence' ? Essence is that which answers the question what a thing is; it is substance considered as definable.
'It is clear that essence is that which is signified by the definition of a thing' (De ente et essentia, 2). In the case of material things 'the word essence signifies that which is composed of matter and form' (ibid.). ioo
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Existence, on the other hand, is the act by which an essence or substance is or has being. 'Existence denotes a certain act; for a thing is not said to exist by the fact that it is in potentiality but by the fact that it is in act' (C.G.,
I, 22, 4).
Essence is the potential metaphysical component in a thing (it is that which is or has being, the quod est), while existence is the act by which essence has being (it is the quo est). This distinction is not, be it noted, a physical distinction between two separable things; it is a metaphysical distinction within a thing. Essence and existence are not two things. There is no objective essence without existence, and there is no existence which is not the existence of something. When Aquinas talks about existence being 'received' or 'limited' by essence
(cf. De ente et essentia, 6), he does not mean that there is a kind of general existence which is divided up, as it were, among individual things. Inasmuch as existence is always, as far as our experience goes, the existence of some essence, of some particular kind of thing, it can be said to be 'limited' by essence; for it is always the existence of a man or of a horse or of a dog or of some other substance.
And inasmuch as the substance, considered as essence, is that which has being, that of which we say that it exists, it can be said to 'receive' existence. But these ways of speaking are not meant to imply either that existence is something apart from an essence or that an essence has objective reality apart from existence. The distinction between them is a distinction within a concrete finite being.
Aquinas does not, as far as I know, make explicit use of the term 'real distinction' in this connexion. But he speaks of a 'real composition' of essence and existence in finite things (De veritate, 27, 1, ad 8), and he says that the distinction between essence and existence in God is only mental (In Boethium de Hebdomadibus, 2), a statement which clearly implies that in finite things the distinction is not only mental. Moreover, he habitually speaks of existence as being other than essence. In my opinion, then, there can be no doubt that Aquinas asserted an objective distinction between essence and existence in finite things, a distinction,
AQUINAS that is to say, which is not dependent simply on our way of thinking and speaking about things. He distinguished the use of the verb 'to be' in existential propositions like 'Peter Brown exists' and its use in descriptive or predicative propositions like 'Man is rational'; but the distinction between essence and existence was certainly not in his view a purely linguistic distinction.
It is manifested in linguistic distinctions, but what is manifested is, he thought, an objective distinction in things and not itself a linguistic distinction. At the same time, if this objective distinction is called a 'real' distinction, this must not be taken to mean a distinction between two physically separable things like two parts of a watch. Before the union of essence and existence to form a concrete and actual thing there was no objective essence and no existence. And their 'separation' simply means the destruction of that thing.
Aquinas' distinction between essence and existence is thus a distinction between the essence and existence of an actual finite being.
It is not a distinction between our idea of the essence of a thing and the thing itself; this distinction is taken for granted. Nor does it mean, for example, that before a given man existed the essence of the man subsisted in some peculiar realm of essences awaiting existence. For Aquinas did not believe in any such ghostly realm of subsistent essences. In a sense the essence pre-existed in God as a divine 'idea'. But Aquinas was well aware that to speak of 'ideas' in God is to speak anthropomorphically and that there is no objective distinction between the divine ideas and the divine being. The existence of the 'divine ideas' and the divine existence are one and the same. And the distinction between essence and existence is not a distinction between God and creatures; it is a distinction within the actual finite being itself. When Aquinas says that existence 'comes from outside and together with the essence forms a composite being' (De ente et essentia, $) he does not mean that a previously 'existing' existence is given to a previously 'existing' essence, which would be sheer absurdity: he means that the act by which an essence has being is caused, the
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cause being external to the thing itself. That which comes into being is an existent substance; but it does not exist simply because it is the sort of thing which it is, for example a man.
Aquinas' way of approaching the matter, however, is sometimes apt to mislead. The De ente et essentia was an early work, and in it Aquinas' way of approaching the distinction between essence and existence was influenced by Alfarabi and Avicenna. 'Whatever does not belong to the concept of an essence or quiddity comes from outside and with the essence forms a composite being. For no essence can be understood without the parts of that essence. Now, every essence or quiddity can be understood without its actual existence being understood. For I can understand what a man or a phoenix is and yet not know whether they exist in nature.
It is clear, therefore, that existence is different from quiddity, unless perhaps there is something whose essence is existence' (De ente et essentia, 5). This passage may suggest that Aquinas founded his distinction between essence and existence simply on our ability to learn the meaning of a word by description without knowing whether there is anything to which this description actually applies. For instance, as we have already seen, if a small boy comes across the words 'elephant' and 'dinosaur' in a book and does not understand them, he may ask his father to explain. And though his father would in practice probably refer to the facts that there are elephants and that there are now, so far as we know, no dinosaurs, this would not be necessary. The meanings of the words could be explained by description without any reference being made to the existence of elephants and the non-existence of dinosaurs. The conclusion might thus be drawn that all that Aquinas is really doing is to draw our attention to our ability to learn the meaning of a word by description without adverting to the question whether anything exists to which the description applies. But Aquinas did not think that this ability is an infallible sign of an objective distinction between essence and existence in the thing named. For he expressly
AQUINAS says that a man can know the meaning of the word 'God' without knowing that God exists.
'It is not necessary that immediately the meaning of the word God is known it should be known that God exists' (C.G., i, n). As Aquinas was convinced that there is no objective distinction between essence and existence in God, he cannot have considered that our ability to learn the meaning of a word by description without knowing whether there is anything to which the description applies is an infallible proof of an objective distinction between essence and existence in the thing named.
If there is no objective distinction between essence and existence in God, then presumably to learn the meaning of the word 'God' involves learning that it means a Being whose essence involves existence. But it does not follow that to learn the meaning of the word 'God' is necessarily to learn that God exists. This would follow only if learning the meaning of the word God involved an intuition or direct apprehension of the divine essence. And Aquinas did not believe that we have anything of the kind.
It would seem, therefore, that we are entitled to interpret the statement that our ability to understand the essence of, say, man without adverting to the existence of men postulates an apprehension of the essence of man, existence not being included
1 Or, better, the mind apprehends the in this apprehension. concrete essence or nature as that which has being, that is, as existing. The distinction between essence and existence is explicitly understood only by philosophic reflection; but it is implicitly present in our direct apprehension of things and implicitly manifested in ordinary language.
Aquinas would therefore presumably justify the essenceexistence language, which doubtless seems so strange to many of us, as being necessary in order to render explicit the implications of ordinary knowledge and ordinary language.
It is not that the metaphysician discovers a new fact, namely that essence is distinct from existence, in the way i. Aquinas did not hold that we ordinarily have direct intuitions of the essences of things.
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that an explorer may discover a hitherto unknown island or flower : it is rather that he makes explicit what is implicitly contained in our apprehension of actual things.
Certain modern Thomists postulate as the foundation of metaphysics an initial metaphysical intuition of 'being' which some philosophers apparently have while others do not, the former being the metaphysicians. But if there is such an intuition, it cannot be equivalent to a privileged mystical experience on the part of metaphysicians, a conception which Aquinas certainly did not admit. Nor can it be equivalent to the communication of a piece of factual information to a select few.
It would presumably be more akin to seeing something familiar 'for the first time' or 'in a new light', in this case to seeing the existential aspect of finite things in a clear light. As Aquinas already believed in God and in divine creation, he was obviously predisposed to see a finite substance as not involving its own existence.
Or, in other terms, he was predisposed to view every existential proposition about a finite thing as a contingent proposition. But he clearly thought that the distinction between essence and existence in finite things can be apprehended apart from knowledge of God's existence.
In a passage already quoted (De ente et essentia, 5) he asserts that 'it is clear therefore that existence is different from essence (quidditas); unless perhaps there is some thing whose essence is existence'. The phrasing of the last part of this statement makes it clear that he did not look on the recognition of the essence-existence distinction as dependent on a previous knowledge of God's existence. Nevertheless as belief in God predisposed him to recognize this distinction, it is easily understandable that he makes no explicit statement about any 'metaphysical intuition', and it may well be that those are right who think that an intuition of this kind is implicitly presupposed. As I have indicated, however, it would be quite foreign to Aquinas' mind to accept the idea of a quasi-mystical 'intuition of being', enjoyed by a select company of metaphysicians. In his view 'that which the intellect first conceives ... is being' (De veritate, 1, 1). Whatsoever
AQUINAS I apprehend, I apprehend as some thing, as a being. But this implicit apprehension of being which accompanies all our mental contact with things is not the 'intuition of being' of which Thomists like £tienne Gilson and Jacques Maritain speak, though it is its foundation and condition. They are talking rather of a conscious advertence to the existential aspect of things, of seeing this aspect in a sharp light, as it were. And it may well be that the prominence attributed in Aquinas' philosophy to the problem of existence presupposes some such conscious 'experience' of what is there for all but of which not all are as vividly conscious as was Aquinas.
I do not pretend that the foregoing considerations eliminate all difficulties which arise in the use of the essence-existence language; far from it. One can scarcely avoid using this language if one is to see the distinction between essence and existence on the plane on which Aquinas placed it, namely on the metaphysical plane. And it can be pointed out that the structure of our language makes it very difficult to speak about the subject without using terms and phrases which appear to 'thingify' essence and existence. None the less, a thorough analysis of the essence-existence language by those who wish to retain it is certainly required. To speak simply of an 'intuition' is scarcely satisfactory. For even if the intuition, interpreted on the lines suggested above, is granted, the language used to render it explicit is still open to critical analysis. Aquinas himself was obviously not called upon to justify the use of a language familiar to his contemporaries, but a term like 'essence' cannot be taken for granted today.
It is one thing to say what Aquinas meant by it; it is another thing to make it acceptable to one's own contemporaries.
However, considerations of space do not permit further development of this theme; and I want to conclude the section with some brief remarks on the question whether Aquinas' doctrine implies that he thought that existence is a predicate.
The assertion of a distinction between essence and existence was not new. Islamic philosophers like Alfarabi
(d. c. i«>6
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950), Avicenna (d. 1037), and Algazel (d. mi) had already made this distinction. But they spoke of existence as an 'accident', though Avicenna saw that it cannot be an accident like other accidents. Aquinas saw this clearly, and for him existence was not an accident at all but that which rendered the possession of accidents possible.
It would be absurd to say, for example, that Peter is white, tall, existing, and amusing. For if Peter did not exist he could be neither white nor tall nor amusing. Existence was for Aquinas the act by which substance has being; and unless it has being it cannot have accidental modifications. He speaks of it as being that which is most intimate and most profound in a thing, being like a form in relation to all that is in the thing (ST., la, 8, 1, ad 4). He does indeed speak of it as a 'perfection', but it is 'the actuality of all acts and thus the perfection of all perfections' (De potentia, 7, 2, ad 9). In other words, existence cannot be numbered among a list of attributes, since it is the foundation of all attributes. Aquinas' language may suggest that it is an attribute of essence; but it is in a real sense the foundation of the essence itself, because without the act of existing the essence would not have being.
It may indeed appear to constitute a contradiction in terms if it is said on the one hand that existence is the act by which essence has being and on the other that essence receives existence. But Aquinas did not look on essence as an existent something which can receive 'existence' as a kind of accident. A thing's coming into being involves the simultaneous production of two inseparable metaphysical constituents, of an essence as determining its act of existence to be the existence of this or that kind of thing, and of existence as actualizing the essence. There is no question of the one principle being temporally prior to the other. As I have said, there are difficulties enough about this conception, but one cannot begin to understand Aquinas' theory if one persists in interpreting him as thinking of essence and existence as two things or as two physical components of a thing. One thing is produced and exists; but in that one thing we must, according to Aquinas, distinguish essence and existence,
AQUINAS which are objectively distinct though they are not distinct as separate or separable things. Aquinas would be the first to acknowledge that though one may predicate existence of essence as far as grammar goes, existence is not and cannot be an attribute in the sense in which other attributes are attributes.
The foregoing outlines of the distinctions between substance and accident, matter and form, essence and existence, all of which illustrate in their several ways the general distinction which runs through all finite being, namely the distinction between act and potentiality, may give the impression that Aquinas' metaphysic consists simply of arid and tortuous discussions, couched in unfamiliar language and without much relevance to the world as we know it. As a conclusion to this chapter, therefore, I want to bring out some implications of his metaphysics, which may perhaps help to render the latter more easily intelligible.
The distinctions between substance and accident and between matter and form draw attention to two features of the world, namely permanence and change. We all speak of things as though they were in some degree permanent.
Although a human being is born and dies and although a tree has a certain span of life, we all speak of the human being and of the tree, which each is alive, as an individual entity.
Even in the abnormal and pathological case of 'split personality' or dual personality we think of the relevant phenomena as happening to a definite human being and as taking place within that human being. We may say, for example,
'he is suffering from schizophrenia', attributing the phenomena to a definite and individual being. At the same time we all think and speak of things both as capable of undergoing change and as actually undergoing change. We ourselves change within certain limits, while retaining our identities. The tree changes, though the changes are predicated of the tree considered as a relatively permanent thing.
Objects with certain names are changed into objects with
THE WORLD AND METAPHYSICS
other names by chemical action for example. Permanence and change are both features of the world as presented in common experience and described in the ordinary language which reflects and expresses this experience. And these features find abstract expression in Aquinas' distinctions between act and potency, substance and accident, form and matter. He may speak in an unfamiliar way, but he speaks about the familiar. He does not construct a static world like that of Parmenides, nor does he present us with a Heraclitean flux; fundamentally he describes the world as it is known by us in daily experience. He presents us with a world which is shot through, as it were, by form, by intelligible structure, and which is therefore to that extent intelligible. On the other hand he presents us with a changing and a developing world. And in emphasizing these aspects of the world he lays too the theoretical foundations for the particular sciences.
If the world were in no way intelligible, science would not be possible, except as a purely mental and unverifiable construct. On the other hand, emphasis on change and development are characteristic of the sciences. One cannot, of course, deduce the conclusions of the empirical sciences from abstract metaphysical principles; nor did Aquinas think that one could. But there is not that cleavage between the world as presented in Aquinas' metaphysics, when distinguished from the contemporary scientific ideas that he accepted, and modern science which there would be, for example, between the philosophy of Parmenides and modern science. Both Aquinas' metaphysics and modern science presuppose the familiar world of common experience, though Aquinas' metaphysics moves on a more abstract plane than the empirical sciences.
This aspect of Aquinas' metaphysics, namely the presentation of a world combining permanence and change, can be called perhaps the construction of the world. That is to say, it presents an abstract theoretical picture of a developing universe which has at the same time sufficient permanence and intelligibility to make knowledge possible. But there is another aspect, which can perhaps be termed the destruction
AQUINAS of the world, if by 'world' one here means a self-sufficient Absolute. This aspect is represented by the distinction between essence and existence. There is a natural inclination to imagine all individual things as existing and acting 'in the world', as though the world were a kind of containing entity, in which other things are situated. For Aquinas, however, the world is the system of interrelated finite substances and not something different from them; and in each finite substance he finds what may be called a radical existential instability, expressed abstractly in the essence-existence distinction. Under this aspect his metaphysic goes in a sense beyond the familiar workaday world, even though he thought of the distinction as reflected in ordinary language.
It also forms a transition to his metaphysical theory about God, to the knowledge of whom metaphysics is, he insists, essentially orientated. This aspect of his metaphysics can be linked, of course, with the systems of other metaphysicians who have concerned themselves with the reduction of multiplicity to unity, of the dependent to the independent or absolute. But it is to be noted that in making the transition from the world to God Aquinas does not, as it were, annul the world of finite substances or turn them into accidents or modes of the Absolute : he relates the finite substances of experience to God, and it is in these concrete things that he finds a relation to a ground of their existence. His 'destruction' of the world is a critique of the idea of the world as a quasi-entity, as a pseudo-Absolute, and not of the things which in their inter-relatedness form the world. How he makes the transition from finite beings to God will be considered in the following chapter. no