The Philosophy of Thomas Aquinas
For a more advanced & comprehensive discussion, see: The Philosophical System of Thomas Aquinas, by Maurice de Wulf
I. The Life of Thomas Aquinas --1225-1274
The "Angelic Doctor" Thomas Aquinas (picture), born of a noble family in Rocca Secca, near Aquino in 1225, was to complete the magnificent synthesis of Scholasticism. As a very young boy, he went to Monte Cassino, the celebrated Benedictine monastery which at the time was headed by one of his uncles. He displayed such brilliance that the monks advised his father to send him to the University of Naples, where he could receive a more advanced education. While in Naples, he entered the Dominican Order. His mother, far from favorable to this move, hastened to Naples; but the Dominicans, fearing her opposition, had already send Thomas to Rome in the hope that he would eventually be able to reach Paris or Cologne.
His brothers captured him on the road and held him prisoner in the fortress of San Giovanni at Rocca Secca, where he remained almost two years while his family tried to dissuade him from following his vocation.
Finally released, he was sent to Rome, then to Paris and Cologne where he studied in the school of Albertus Magnus. There he was introduced to the study of Aristotelianism and completed his theological studies. In 1252, Thomas Aquinas was sent to Paris to further his studies and then to teach, which he continued to do until 1260. In that year he returned to the Roman province of his Order, where he was given various offices of administration and education in the province.
In 1269 he was again in Paris, where he carried on the controversy against the Averroism of Siger of Brabant. In 1272 he went to Naples to assume the chair of theology at the university there. At the beginning of 1274 he set out with a companion for the Council of Lyons, but died en route, at the Cistercian monastery of Fossa Nuova near Terracina, on March 7, at the early age of forty-nine. He was proclaimed a saint by the Church, and by posterity has been acclaimed as the Angelic Doctor.
II. The Works of Thomas Aquinas
The works of Thomas Aquinas may be conveniently divided into four groups:
1. COMMENTARIES on the Logic, Physics, Metaphysics, and Ethics of Aristotle; on the Scriptures; on Dionysius the Areopagite; on the Four Books of Sentences of Peter Lombard.
2. SUMMAE The Summa contra Gentiles (A Summary Against the Gentiles), founded substantially on rational demonstration; The Summa Theologica (A Summary of Theology), begun in 1265, and remaining incomplete because of Thomas' early death.
3. QUESTIONS Quaestiones Disputatae (Disputed Questions): De Veritate (On Truth), De Anima (On the Soul), De Potentia (On Power), De Malo (On Evil), etc.; Quaestiones Quodlibetales (Questions About Any Subject).
4. OPUSCULA (selected examples) De Ente et Essentia (On Being and Essence); De Unitate Intellectus (On the Unity of the Intellect), written against the Averroists; De Regimine Principum (On the Rule of Princes).
III. An Introduction to His Doctrine
Thomas Aquinas was the first to recognize the fact that Aristotelian intellectualism would be of great help for the study of philosophy as well as theology. But the introduction of Aristotle's works involved the solution of the disputed question of the relationship between philosophy and theology.
At the time of Aquinas, besides the Averroist theory of the double truth, by virtue of which philosophy and theology were not only separate but opposed, there was also Augustinianism, which was largely accepted in the School and held that no real distinction between philosophy and theology was possible.
This confusion between philosophy and theology was a necessary consequence of the theory of illumination, according to which the human intellect was considered incapable of abstracting intelligibles from the data of experience, but rather received them from the Divine Teacher. This Teacher communicated to the intellect the intelligibles regarding the material things of the surrounding world as well as those concerning the invisible and supernatural world. Thus the human intellect was capable of understanding not only material things but also the mysteries of religion. Hence no distinction between philosophy and theology was possible.
Thomas Aquinas sharply opposed both Averroism and Augustinianism. He did not accept the theory of the double truth, not only because of its irreligious consequences regarding the mortality of the human soul, but because he was convinced of the falsity of such a theory.
For Aquinas, what reason shows to be true is absolutely true, so that the opposite is absolutely false and impossible.
If religion, therefore, teaches something that is opposed to reason, as the Averroists maintained it does, it would teach what is absolutely false and impossible.
Two contradictory truths cannot be admitted; truth is one, either in the field of reason or of religion. The two fields are separate but not opposed. There are religious truths -- such as the mystery of the Trinity and the Incarnation -- which the human intellect cannot penetrate; and these truths must accepted on the authority of revelation.
Parallel to them, there are natural truths concerning this visible world which are intelligible to the human mind and are the object of philosophy and science.
To the question whether there also some truths which at the same time are revealed and open to rational demonstration, Aquinas answers yes. Such truths are the existence of God and the immortality of the human soul, which are demonstrable by reason. God revealed them, however, in order to make these truths accessible to the minds of those who cannot attain philosophical investigation.
But Aquinas also opposed Augustinian illumination. Granting that the human soul is intellectual by nature, he maintains that the human intellect by its natural power is able to draw the intelligibles from material objects. Besides its own natural power, the human intellect does not need any special divine assistance in abstracting the intelligibles from the data of experience.
Indeed, if Aristotle, a pagan philosopher, could establish a systematic and rational interpretation of the visible world, we must admit that the human intellect has the power of knowing some fundamental principles and is capable of drawing therefrom a perfect science without divine assistance.
Moreover, since with Aristotle we know what rational demonstration means, we can see how vain is the assumption of the Augustinians that the mysteries of faith can be demonstrated "by means of necessity." The truths of faith are above human understanding. They are the object of faith and not of science. Hence philosophy and theology are distinct and this distinction must be retained.
Although distinct, they are related. Philosophy shows the necessity of faith by demonstrating the existence of God and the immortality of the soul. Theology on the other hand helps philosophy to reflect more deeply and to correct itself if some philosophical conclusion is contrary to the mysteries of faith.
IV. Theory of Knowledge (Epistemology)
To explain the process of knowledge, Thomas Aquinas has recourse neither to the innate ideas of Platonism nor to the illumination of Augustine. Instead, he postulates a cognitive faculty naturally capable of acquiring knowledge of the object, in proportion to that faculty. Agreeing with Aristotle, he admits that knowledge is obtained through two stages of operation, sensitive and intellective, which are intimately related to one another. The proper object of the sensitive faculty is the particular thing, the individual; the proper object of the intellect is the universal, the idea, the intelligible.
But the intellect does not attain any idea unless the material for that idea is presented to it by the senses: "Nihil est in intellectu quod prius non fuerit in sensu." The two cognitive faculties, sense and intellect, are naturally capable of acquiring knowledge of their proper object, since both are in potency -- the sense, toward the individual form; and the intellect, toward the form of the universal.
The obtaining of the universal presupposes that the sensible knowledge of the object which lies outside us comes through the impression of the form of the object upon the sensitive faculty. This is likened to the impression of the seal upon wax. Upon this material impression the soul reacts according to its nature, that is, psychically, producing knowledge of that particular object whose form had been impressed upon the senses. Thus the faculty which was in potency is actuated with relation to that object, and knows and expresses within itself knowledge of that particular object.
But how is the passage made from sensitive cognition to that which is intellective? Or, rather, how is the individual form which is now offered by sensible cognition condensed into an idea and thus made the proportionate object of the intellect?
To understand the solution to the problem, it is necessary to recall the theory of Aristotle which Aquinas makes his own; that is, that the individual form is universal in potentia. It is the matter which makes the form individual. Hence if the form can be liberated from the individualizing matter, or dematerialized, it assumes the character of universality.
According to Thomas Aquinas, this is just what happens through the action of a special power of the intellect, i.e., the power by which the phantasm (sense image) is illuminated. Under the influence of this illumination, the form loses its materiality; that is, it becomes the essence or intelligible species (species intelligibilis). Thomas call this faculty the intellectus agens (agent intellect), and it is to be noted that for Thomas the "intellectus agens" is not, as the Averroists held, a separate intellect which is common to all men.
For Aquinas, the agent intellect is a special activity of the cognitive soul, and it is individual and immanent in every intellective soul. The "species intelligibilis" is then received by the intellect, which is called passive since it receives its proper object, and become intelligible in act. Note that according to Aquinas the form, both intelligible and individual, is not that which the mind grasps or understands (this would reduce knowledge to mere phenomenalism), but is the means through which the mind understands the object (individual form) and the essence of the object ("forma intelligibilis").
Knowledge thus has its foundation in reality, in the metaphysical.
Furthermore, since the cognitive faculty is in potency, when it becomes actuated, it becomes one with the form which actuates. Thus it may be said, in a certain sense, that the intellect is identified with the determined form which it knows.
For Aquinas all the data of sense knowledge and all intelligible things are essentially true. Truth consists in the equality of the intellect with its object, and such concordance is always found, both in sensitive cognition and in the idea. Error may exist in the judgment, since it can happen that a predicate may be attributed to a subject to which it does not really belong.
Besides the faculty of judgment, Aquinas also admits the faculty of discursive reasoning, which consists in the derivation of the knowledge of particulars from the universal. Deductive, syllogistic demonstration must be carried out according to the logical relationships which exist between two judgments. In this process consists the science which the human intellect can construct by itself, without recourse either to innate ideas or to any particular illumination.
V. General Metaphysics
Aquinas accepts the general principles of the metaphysics of Aristotle, for whom there are two principles of being, potency and act. Act signifies being, reality, perfection; potency is non-being, non-reality, imperfection. Potency does not, however, mean absolute non-being, but rather the capacity to receive some perfection, the capacity to exist, as Aristotle taught.
The transition from potential to actual existence is becoming, that is, the passage from potency to act. Outside of becoming there exists Pure Act, the absolute reality and perfection upon which all becoming depends. The general principle of metaphysics, potency and act, applied to that part of becoming in which matter is already existent, is specified in a second principle, the principle of matter and form.
Matter which in potency is not be understood as pure nothingness, but is as a being having in itself no determination. Thus matter is to be conceived of as the substratum of form. The form which is in act gives to the matter specific determination, reality, perfection -- that which we mean when we ask what is such and such a thing.
The union of matter and form constitutes or gives place to the substance, to the "totum," the individual. Relative to the question of the principle of individuation, or the question of how it happens that a determined specific form can give place to a multiplicity of individuals of the same species, Aquinas affirms that the principle of individuation is matter -- not matter considered abstractly, pure matter, but matter signed by quantity, or that concrete matter in which the new form is produced.
If prime matter and substantial form are sufficient to constitute the "totum" (the substance), then this latter, to be perfect, can and must receive other or secondary forms, i.e., accidental forms which give new determination to the substance (quantity, quality, etc.). The accidents, since they are determinations of the substance, are ordained to the substance and depend on it.
The concept of matter and form gives us an explanation of how a thing becomes, but does not tell why it becomes. To present us with the why of becoming, it is necessary to have recourse to a third concept -- that of efficient cause -- which produces such a determination of form in matter and is the reason why this particular form arises in the matter.
Finally, to give us the reason why the efficient or acting cause or agent is made to bring about the union of this form in this matter, we need a fourth element, the concept of end. End (finis) indicates the purpose the agent has in mind when he acts, or gives actuation to this form in this matter.
Final cause hence indicates the end, and also the order according to which the agent is determined to act: First in intention, the purpose or end is last in execution -- the purpose of the agent is achieved only when the entity is completed in its material element and its substantial and accidental forms. Thus for Aquinas, as for Aristotle, the concepts explaining reality are reduced to the concepts of the four causes -- material, formal, efficient, and final.
VI. The Existence of God (Theodicy)
The Five Ways
The search for God and His relationship with the world was as fundamental in the Middle Ages as it was at any time during the history of Christian thought. At the time of Aquinas, Augustinianism was the most appreciated doctrine in the school of philosophy at the University of Paris. In virtue of illumination, which is the central point of Augustinianism, the human soul could have an intuitive knowledge of God. Indeed the intellect had only to reflect upon itself to find the presence of the Divine Teacher.
Thus the existence of God was proved a priori by means of necessary reason. Obviously, if the presence of the ideas of absolute truth and good in our mind must be explained by the direct suggestion of God, we do not need any other proof of God's existence.
But, according to Aquinas, any natural intuitive knowledge of God is precluded to man. For us, only the visible world, which is capable of impressing our senses, is the object of natural intuitive knowledge. Thus any argument a priori for the existence of God is devoid of validity. For Aquinas, the existence of God needs to be demonstrated, and demonstration must start from the sensible world without any prejudice. 4 Such demonstrations are possible and are accommodated to anyone who is simply capable of reflecting. There are five ways in which the human intellect can prove the existence of God. All have a common point of resemblance. The starting point is a consideration of the sensible world known by immediate experience. Such a consideration of the sensible world would remain incomprehensible unless it was related to God as author of the world.
So each argument might be reduced to a syllogism whose major premise is a fact of experience, and whose minor premise is a principle of reason, which brings to light the intelligibility of the major premise.
It is interesting to note that Aquinas uses the Aristotelian principle of the priority of act over potency for the first three arguments. Where there is a being in change, i.e., passing from potency to actuality, there must be another being actually existent, outside the series in change, whether this series is considered to be finite or infinite.
Aquinas formulates this principle in three different ways according to the three aspects of reality taken into consideration. For the first way the formulation is: What is moved, is moved by another; for the second way: It is impossible for something to be the efficient cause of itself; for the third way: What is not, cannot begin to be, unless by force of something which is. The fourth way takes into consideration many aspects of reality, which, when compared with one another, show that they are more or less perfect. The principle of intelligibility is the following: What is said to be the greatest in any order of perfection is also the cause of all that exists in that order.
The fifth way takes into consideration the order of nature: Where there is a tendency of many to the same end, there must be an intellectual being causing such an order. Let us set forth the schematic structure of the five ways: Our senses attest to the existence of movement or motion. But every motion presupposes a mover which produces that movement. To have recourse to an infinite series of motions is not possible, for such an infinite series does not and cannot solve the question of the origin of the movement. Hence there exists a first mover that moves and is not itself moved. This is God.
Some new thing is produced. But every new production includes the concept of cause. Thus there exists a first cause which is itself not caused. This is God. Everything in the world is contingent; that is, it may or may not exist. We know from experience that all things change in one way or another. But that which is contingent does not have the reason of its existence in itself, but in another, that is, in something which is not contingent.
Hence there exists the necessary being, God. The fourth way takes into consideration the transcendental qualities of reality, "the good, the true, the noble," and so forth, which we find in things to a greater or lesser degree. But transcendental qualities are nothing other than being, expressed through one of its attributes; hence things under our experience are beings to a greater or lesser degree. But the greater and lesser are not intelligible unless they are related to that which is the highest in that order; and what is the highest is also the cause of all that exists in that order. Therefore there exists the highest degree of being and it is the cause of all limited being. This is God. Order exists in the world about us. Hence there must exist an intelligence responsible for the order of the universe. This is God.
Thus, in brief, we have Aquinas' five proofs for the existence of God; proofs from the notion of motion, cause, contingency, perfection, and order. The proofs for the existence of God are also means of knowing something of God's essence. This knowledge, however, remains always essentially inadequate and incomplete.
One way of knowing God is the way of negative theology, that is, by removing from the concept of God all that implies imperfection, potentiality, materiality. In other words, by this method we arrive at a knowledge of God through considering what He is not.
A second method is that of analogy. God is the cause of the world. Now every object reflects some perfection of the cause from which it proceeds. Hence it is possible for the human mind to rise to the perfections of God from the consideration of the perfection it finds in creatures. This it does, naturally, by removing all imperfection and potentiality from the creatures considered. The resultant idea of the nature of God is thus had through analogy with the perfections of the created universe.
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1. Contra Gent., I, 7.
2. Summa. Theol., Part I, q. I, a.1.
3. Summa Theol., Part I, q 1, a. 1; q. 12, a. 4; q. 32, a. 1; In Primum Librum Sent., q. 1, a. 1 and 2.
4. Summa Theol., Part I, q. 2, a.1; Contra Gent., I, 11.
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Author: Cultural Rafed Foundation
