Thomas Aquinas and Aristotle's Metaphysics

“All men by nature desire understanding.” This is how Aristotle opens his famous Metaphysics, one of the greatest philosophical works ever produced. The thirst for knowledge has always occupied Western man at least since the time of Thales, and even though many different views and opinions about what knowledge is and how it can be gained have abounded throughout Western philosophy up to this very day, the fact that so many men have dedicated their lives to seeking knowledge on all sort of different planes is evidence that the quest for knowledge has occupied a supreme position among human endeavors from the earliest times.
In this essay, I will be taking a look at Aristotle’s metaphysics of causality and change and compare and contrast it with the conception of causality of Thomas Aquinas. Since Aquinas’ metaphysics cannot be understood unless we are familiar with the Aristotelian theories . . . on matter and form, on causality, and on potency and act,”[2] I will first have to explicate the relevant parts of Aristotle’s metaphysics in order then to consider the saint’s modifications and additions as regards his theory of causality. Finally, I shall reflect on these two great philosophers and offer some concluding thoughts on their contributions to philosophy.
Though the first philosophers, the Pre-Socratics, were fairly primitive, it didn’t take long for them to figure out that there must be more to the world than meets the eye. Even the very first philosopher, Thales, supposed that if change occurs in the world, there must be something underlying those changes which itself is always permanent. This started the quest for the so-called Urstoff, and this is what got philosophy going, as early as ca. 600 B.C. It is the first testimony we have that Western man indeed “desired to know.”
To Aristotle it was clear that “though all men desire to know, there are different degrees of knowledge.”[3] He distinguished between three categories, namely emporia, tékhne, and Sophia. Emporia refers to experience; it “is an inanimate knowledge of [particular] things . . . in an immediate and concrete way, something which gives us information only about the particular thing.”[4] Tékhne, which is “art” or “technique,” is a higher mode of knowledge, and a man who has reached this stage “knows how to do things, knows what means to use in order to obtain the desired results.”[5] The highest mode of knowledge, however, is Sophia, “Wisdom.” Wisdom is such that that it can “tell [us] what things are and why they are”; [6] it tells us about a thing’s first principles and causes. Surely, then, in order to come to such a high level of knowledge, one must practice a particular science which concerns itself with just such first principles and causes—and this science Aristotle called “metaphysics.” For Aristotle, metaphysics was “desirable for its own sake,” [7] and this assertion were confirmed by the fact that the Pre-Socratic philosophers “began to wonder at things, to desire to know the explanation of the things they saw . . . notion account of any utility that knowledge might possess.”[8]
While the name for this science originated from the fact that Aristotle had his writings on it located simply after his writings on physics, [9] there is a sense in which the term can also be interpreted to refer to such objects of study which are “beyond the physical,” so to speak, and hence metaphysical. Unlike the other sciences, metaphysics studies what exists as such, that is “being qua being,” [10] as the traditional formulation has it. Since it considers the very first principles of things, and “the sciences with fewer principles are more accurate than those which use additional principles,” [11] it is entirely fitting to make it “first philosophy” and thus superior to any other science.
In his aspirations for wisdom, then, Aristotle engaged in metaphysics. His zeal resulted from the wonder, the aporía, which his predecessors had shown, and which intrigued him just as much. Aristotle was convinced, however, that his predecessors’ philosophies were incomplete and inadequate, especially as far as the paradox of change was concerned. The problem of change which the ancient philosophers faced is simply the following: “If we say that A changes to B, we seem to be saying that A is both itself and not itself. It must be A, for we say, ‘A changes’; it cannot be A, because we say it is B. If water is water, it is not ice; if it is ice, it is not water.”[12] Aristotle was resolved to master this enigma once and for all, but, unlike Parmenides or Plato, he wanted to do it in a way consistent with empirical reality, i.e. with what we experience.
To explain how change occurs, Aristotle reflected on how we know things. It was clear to him that a thing is best known when we do not merely know what color, size, or shape it has, but when we know what it is. Thus, the mind distinguishes “a thing from all its qualities and focuses upon what a thing really is, upon its essential nature.”[13] This substratum Aristotle called ousía, “substance,”[14] and it is this in particular with which metaphysics concerns itself. Aristotle defined substance as “that which is not asserted of a subject but of which everything else is asserted.”[15] For Aristotle, then, all individual things are substances. Now, Aristotle believed that all substances have two aspects: they are necessarily composed of “matter” and “form”—they are “hylomorphic.”[16] By “form,” Aristotle meant the “properties [a substance] with other particulars” (e.g. being human or being a horse), whereas by “matter” he denoted the thing’s individuality—“that about it which makes it this horse or this man.”[17]Neither matter nor form can exist all by itself; that is, we do not find in the world formless matter or matter less form. This is the reason why all substances are holomorphic for Aristotle.
With this doctrine of substance, Aristotle had already made some progress in his quest for explaining change, but this was only a prerequisite to a more elaborate theory. He observed that “substances develop through time (that is, they grow),” [18] and so there seems to be a sort of movement, or striving, in every substance, which he called “entelechy.”[19] This fact led Aristotle to redefine form and matter as actuality and potentiality: “In order to think effectively of a substance as it endures, yet changes, we must reinterpret matter and form as potentiality and actuality.”[20] What a substance is really or actually right now is its actuality—for instance, I am sitting on an actual chair. Yet, what a substance has the prospect to become is its potentiality—for instance, an actual boy is a potential adult. What is crucial to this notion is that whatever possesses potentiality must possess actuality; that is to say, in order for there to be a potential Y, there must be an actual X. There is no such thing as pure potentiality, for in order for anything to be able to become something else, it must be something already.
Armed with his conceptions of holomorphic substance, potentiality, and actuality, Aristotle was finally able to make sense of the intriguing phenomenon of change:
The individual A turns out on analysis to be a complex; it is a substance, a formed matter. During its change into B some part of A endures unchanged and some part of A alters. What endures is A’s matter; what changes is its form. [21] This, then, is how Aristotle could explain how a chunk of marble could eventually become a statue. Its form was changed while its matter remained the same—its potential to be a statue was actualized.
With this account of change, Aristotle was able to make sense of change and explain substances to a certain extent. However, he still wondered if not perhaps other questions could be asked about substances. For instance, besides asking “What is it?” (Form) and “What is it made of?” (Matter), it made sense to Aristotle to further inquire, “Who made it?” and “What is it for?” Having these questions answered would shed more light on the reason for a thing’s existence, he was convinced, and could so help in the acquisition of Wisdom. The responses to these questions Aristotle entitled “causes.” What we mean nowadays by “cause” is usually an event that precedes an effect, but here the word “cause” is used in a looser sense than we moderns are used to; it means essentially “reason for being” or “explanation.” For Aristotle, then, there are four causes, or reasons, for everything that exists. We can ask at least four questions concerning any entity, and the answers we get will give us a better understanding of the being we are investigating. These four questions can be asked concerning anything, and the responses to them “represent therefore a broad pattern or framework for the total explanation of anything or everything.”[22]
Aristotle’s four causes are traditionally classified as “(1) the formal cause, which determines what a thing is, (2) the material cause, or that out of which it is made, (3) the efficient cause, by what a thing is made, and (4) the final cause, the ‘end’ for which it is made.”[23] To use a classic example, let us apply these four causes to an object of art, say, a statue. In the order just listed, the four causes would be: “(1) a statue (2) of marble (3) by a sculptor (4) for a decoration.”[24] However, the four causes do not just apply to man-made artifices; they can also be used to explain “natural objects, in which no conscious purpose is at work,” [25] and so it is clear that for Aristotle, the four causes can be predicated of anything whatsoever. Now, while it is easy for us to accept the understanding of efficient cause and material cause, because they are easily understood, the notions of formal and final cause might raise some questions, so I will elaborate on those a bit.
The formal cause denotes the essence of a thing, or its form—it is that which a thing strives to be. In the case of a work of art, it exists both in the mind of the artist, who is the efficient cause, as well as in the matter, the material cause, itself. To go back to our example of a marble statue, the idea of the “statue” must exist first in the mind of the sculptor and also somehow in the marble, or else there would not be a marble statue in the end. This is what Aristotle refers to as the formal cause.
The final cause, on the other hand, is a cause, or explanation, in terms of the end for which something is made or done, and with the onslaught of the scientific revolution in the 1600’s and the secularization of science throughout the modern period, it was basically buried as a useless and superstitious add-on to the newly-found scientific explanations of things and hence rejected. That is why the final cause is now wholly alien to the modern reader. However, in Aristotle’s day, things were different and it was not unusual to look for the purpose or end of a thing, especially since his teacher, Plato, had already introduced people to a “doctrine of finality,” which stated that “the final cause of becoming is the realisation . . . of the Good.”[26] It was perhaps this insight of Plato which motivated Aristotle to ask for a purposeful end, or télos, as it is called in Greek,[27] concerning entities in the world. Statues, for instance, are usually made for some end—for decoration, beautification, or some religious purpose. If the desire for decoration, beautification, etc., did not exist, the statue would not come to be. After all, no one makes a statue for no reason; even if one were to make a statue just for its own sake, there would still be a reason, the reason than being “its own sake.” It is in this sense that we are to understand the final cause. But again, just like the other causes, the final cause does not apply merely to human artifacts but also to natural objects, such as plants. For Aristotle, even entities like flowers, trees, etc., had a particular end to which they were striving. Professor Samuel Stumpf explains that:
Although nature does not, according to Aristotle, have “purposes” in the sense of “the reason for,” it does always and everywhere have “ends” in the sense of having built-in ways of behaving. For this reason, seeds sprout and roots go down . . . and plants grow and in this process of change move toward their “end,” i.e., their distinctive function or way of being.[28]
Thus, Aristotle infers, it is fitting to ascribe a final cause to all things, human creations as well as natural objects.
It may now be evident that this notion of final causality, of the télos of things, is inherently connected with Aristotle’s conception of potentiality, for if “the end of an acorn is to be a tree, in some way the acorn is only potentially a tree but not actually so at this time,” [29] and thus by realizing its final cause, the acorn becomes an oak tree by actualizing its potential.
Certainly, all of this is more or less abstract, but this is precisely why knowledge of it leads to Wisdom, to Sophia, not just to tékhne or emporia, and that’s why people ought to esteem the man of Wisdom, who reaches this highest level of knowledge through metaphysics, or first philosophy.
Having examined some essential components of Aristotle’s metaphysics, we can now turn to St. Thomas Aquinas. When the Angelic Doctor came on the scene in the mid-1200’s, his incorporation of Aristotelian philosophy into the Christian faith at first met with serious consternation and criticism among his disciples. Frederick Copleston calls Aquinas’ move “bold” and “modern,” yet at the same time “of the greatest importance for the future of Scholastic philosophy.”[30] In fact, now looking back, an argument can be made that the incorporation of Aristotelianism into scholasticism was most prudent, for though it was a “philosophy, a metaphysics . . . based on radically different, non-Christian, suppositions,” at the same time it was “a philosophy which . . . in many senses seem(ed) to be truth.”[31] It seemed clear to the saintly doctor that “Aristotle’s thought must be assimilated into Christian philosophy,” [32] and thus he only “adopted Aristotelianism as an instrument for the expression of his [thoroughly Christian] system,”[33] and in fact he did so to such an extent that it is not uncommon in Catholic philosophical circles to speak of Aquinas as having “baptized” Aristotle.
With this background in mind, we can now approach St. Thomas’ alignment of Aristotle’s philosophy with his Catholic faith. I shall restrict myself to discussing Aquinas’ initiation of a distinction between essence and existence, as well as his addition of a fifth cause, the exemplary cause, as a result of that distinction.
As we have seen already, Aristotle thought of all individual existing things as hylomorphic substances. A consequence of this view is that, for Aristotle, all individual substances are material; there is no such thing as an immaterial substance, since substances are necessarily composed of form and matter.[34] Aquinas’ Catholic faith, of course, did not permit him to adopt this Aristotelian view since the Catholic Church teaches and Aquinas was convinced of the existence of angels, wholly immaterial beings.
St. Thomas thought that Aristotle’s division of individual substance into form and matter was not sufficient, therefore, since it could only explain finite corporeal substances (which he referred to as “composite” substances),[35] but not finite immaterial substances (which he referred to as “simple” substances),[36] such as angels, the existence of which, Aquinas was convinced, is dictated to us even by sheer reason.[37] Now, for Aristotle, the essence of a thing was its substance (as opposed to its accidents)[38] and thus necessarily composed of matter and form. Aquinas was unable to accept this view in so far as he realized he could not extend these concepts alone—without modification—to simple substances. Hence, the Angelic Doctor insisted that the essence of a thing is not necessarily its substance. Instead, he believed that as regards composite substances, their essence is indeed their matter and form—“The term essence, used with respect to composite substances, signifies that which is composed of matter and form”[39]—, but as far as simple things are concerned, “the essence . . . is form alone.”[40] Thus, there is a fundamental distinction between the essence of a composite substance and that of a simple substance for Aquinas.
Now, Thomas realized that although a thing must have an essence, it need not necessarily exist:
Whatever is not in the concept of the essence or the quiddity comes from beyond the essence and makes a composition with the essence, because no essence can be understood without the things that are its parts. But every essence or quiddity can be understood without understanding anything about its existence: I can understand what a man is or what a phoenix is and nevertheless not know whether either existence has in reality. Therefore, it is clear that existence is something other than the essence or quiddity. . . .[41] Thus, Thomas drew another crucial distinction, namely one between essence and existence: they are fundamentally distinct—except in God, but that shall not concern us here—, since just because something has an essence doesn’t guarantee its existence. Aquinas defined existence as that in virtue of which any finite thing has actual being:
In things composed of matter and form, neither the matter nor the form nor even being itself can be termed that which is. Yet the form can be called that by which it is, inasmuch as it is the principle of being; the whole substance itself, however, is that which is. And being itself is that by which the substance is called a being.[42] The difference between essence and existence is very important because by insisting that not every individual finite being needs to be material, Thomas had thrown out Aristotle’s explanation of change, which, after all, was based on form and matter, reinterpreted as actuality and potentiality.
To retrieve a rational explanation of change, then, Aquinas reinterpreted essence and existence as corresponding to potentiality and actuality, just as Aristotle had done with matter and form: “Existence [stands] to the essence as act to potentiality,” [43] in the sense that the “essence is a potency with respect to the act of existence, because only those things are fully designated as substantial beings that have received existence.”[44] In other words, every finite being, whether material or not, is composed of essence and existence, and “that which actualises the essence is existence.”[45] Essence and existence are so interrelated that neither can subsist without the other: “There is no essence without existence and no existence without essence; the two are created together, and if its existence ceases, the concrete essence ceases to be.”[46]
Hence, to remedy Aristotle’s shortcomings and apply his philosophy to the Christian faith to support the latter, the Angelic Doctor modified the meaning of essence regarding substance and added the notion of existence. For Aquinas, then, the “essence of a corporeal being is the substance composed of matter and form, while the essence of an immaterial finite being is form alone. . .,”[47] while “that by which a material substance or an immaterial substance is a real being (ens) is existence (esse). . . .”[48]
With this in mind, we can now fully appreciate St. Thomas’ views on causality. With Aristotle, the saint affirmed the four classic causes: formal, material, efficient, and final. However, given Thomas’ addition of the distinction between the concepts of essence and existence, the saintly doctor was now able to add a fifth cause, the “exemplary cause,”[49] which extended Aristotle’s traditional notion of causality and made it more comprehensive, more precise, and more complete.
Exemplary causality is defined as “the causal influence exercised by a model or an exemplar . . . on the operation of an agent.”[50] To return to our example of a statue, the sculptor must already have in mind the statue he wants to create in order for him to be able to do just that,[51] and in order for there to be a statue in the end: “Before something begins to be in reality, it is already in the mind of the agent.”[52]This blueprint in the mind of the artist is an example of what St. Thomas called the exemplary cause. Thus, the idea a man working on a project has in mind can be an exemplary cause in relation to that project, and God would be considered the exemplary cause of all of creation.[53]
Now, it may seem that the exemplary cause bears some resemblance to the efficient, formal, and final causes, and so it is important to note the differences between them:
Because of this relation to the agent [exemplary causality] is referred to as his operative idea . . . and so is conceived as a type of productive or efficient causality; because of the relation to form it is alternatively thought of as an extrinsic formal cause and so is classified as a type of formal causality. However, since the exemplary cause is extrinsic to the effect and exerts its influence mainly as an idea in the intentional order, it would seem to be more proper to view it as a type of final causality.[54] This is not to say, however, that the exemplary cause is the same as the final cause. The difference lies in the fact that the “final [cause] moves the will” whereas “the exemplary [cause] guides the intellect.”[55]As noted above, the statue the sculptor makes must, in some sense, already exist in the mind of the artist. It is in this sense that we are to understand the assertion that the exemplary cause “guides the intellect.”
Aristotle’s traditional four causes only applied to actuality, i.e. to existing things, and not to potentiality, i.e. to essence. Aquinas’ distinction between essence and existence, however, completed the theory of causality by adding the exemplary cause to Aristotle’s closed circle of four causes. As a consequence, Thomas distinguished more accurately the realm of possibility or essence from that of actuality or existence.[56] St. Thomas’ conception of exemplary causality thus enriches and refines Aristotle’s four causes, because unlike the formal, material, efficient, and final causes, the exemplary cause refers to ideas, to the realm of essences and potentiality, since it is “a form or idea in imitation of which something comes to be.”[57] This distinction Aristotle was unable to draw due to his conviction that all individual substances are necessarily hylomorphic.
Given the similarities and differences between Thomas and Aristotle, it now remains to evaluate their contributions to philosophy. There is no doubt that St. Thomas owes his fundamental philosophical outlook to Aristotle, for, as one can see, “the Thomist synthesis is unified by the application of fundamental Aristotelian principles.”[58] Aquinas gladly acknowledged his indebtedness to Aristotle, often referring to him throughout his works simply as “the Philosopher.”[59] This fact has raised questions in different circles as to how a Christian theologian of Thomas’ caliber could be so devoted to a pagan philosophical system, and in fact that’s precisely what triggered the heated controversy in Aquinas’ day. The answer to that is simply that Thomas was convinced that much of Aristotle’s thinking was true. Frederick Copleston emphasizes that St. Thomas “would certainly not have adopted the system of a pagan philosopher, had he not considered it to be in the main a true system.”[60] For the saint, the question was not whether Aristotle’s basic philosophical tenets originated in a pagan mind, but rather whether they were true or not, and, if so, whether they could aid in explicating reality and Christian doctrine. But this doesn’t mean that Thomas accepted everything from Aristotle uncritically. When looking at the commentaries Thomas wrote on Aristotle’s works, it is immediately obvious that “Aquinas was not a blind follower of Aristotle [but] parted way with him when he deemed it necessary,”[61] as this paper has contributed to demonstrate. Besides, the saintly doctor also made use of the observations and contributions of other philosophers, such as the Neoplatonists, St. Augustine, and some Islamic thinkers such as Avicenna and Averroës.
As far as this paper’s consideration of Aristotle’s and Thomas’ notions of causality is concerned, one may raise the question as to whether the Angelic Doctor’s modifications have contributed anything significant to the classical Aristotelian doctrine. For someone deeply grounded in the modern or postmodern philosophical traditions, while perhaps appreciating the difference between essence and existence which Aquinas spelled out, it may seem hard to see any considerable or substantial significance in his introduction of the exemplary cause as resulting from the essence-existence distinction. However, we must keep in mind that Thomas worked within the medieval paradigm, one that was much closer to—if not almost identical with—the classical paradigm than it would be to the modern one. Back then, metaphysics was regarded as the queen of all sciences, and I am sure that any sort of novelty was of utmost importance, at least in the philosophical circles, for just by looking at the kinds of questions St. Thomas raised and answered in his Summa Theologica, one can immediately sense that no detail was considered too small or “nitpicky” to have a disagreement about.
As far as the exemplary cause itself is concerned, I feel that it could be understood in such a sense that it would seem to be a kind of synthesis of efficient, formal, and final cause, inasmuch as it does bear resemblance to each of them to an extent. To say, then, as Aquinas does, that God is the “first exemplar [sic] cause of all things”[62] would reemphasize that God is the ultimate cause of all being, that he is the beginning and the end of all that exists. And God could even be said to be the material cause of all things to the extent that matter was created by God-acting-as-efficient-cause, and thus all being has its origin—and end—in God. This is a typical medieval attitude, and thus it seems to me that my own reflection would be very much in alignment with the medieval spirit.
As the scientific revolution exerted its influence on the philosophical world in the 1600’s, causality was reduced from Aquinas’ five causes to one single cause, namely the efficient cause. The term “cause” became synonymous with “event preceding an effect,” and the classical meaning of cause as “explanation” or “reason for being” was basically extinguished. I believe that this is unfortunate because the classical notion is much richer and can give us a deeper understanding of those things that exist in the world and explain especially why they exist and how they exist. Modern natural science, of course, does not even consider the question of why, and thus it can never give us an answer in this regard.
And yet, it is one of the most fundamental questions any inquiring mind wishes to have answered, even though this desire, of course, can be suppressed, as it had been for decades after Kant in such traditions as logical positivism and analytical philosophy. It was Martin Heidegger who woke us up again from what I call our “positivist slumbers” by opening his opening book” An Introduction to Metaphysics” with the intriguing question, “Why is there something rather than nothing?”[63] Thus, I am convinced that authentic metaphysics,[64] though perhaps suppressed at times, will inevitably rise again and again because it remains man’s most proficient tool to understand reality in his never-ending quest to satisfy his “desire to know.”