[1964. In Encyclopedia of Christianity. Edwin A. Palmer, ed. Wilmington, Delaware: National Foundation for Christian Education.]
By his genius Thomas Aquinas persuaded the church to abandon Augustinianism in favor of the philosophy of Aristotle, whose works had begun to appear in the W during the latter half of the 12th century. In 1879 Pope Leo XIII officially made Thomism the basic philosophy of the Roman Church.
One of Thomas’ objections to Augustinianism was its inadequate sense of logical demonstration. Anselm had merely deceived himself when he claimed that the atonement could be demonstrated apart from the Scriptures. Reason, i.e. man’s natural cognitive powers working from the perceptible universe, cannot demonstrate the Trinity, temporal creation, original sin, the incarnation, the resurrection of the body, or heaven and hell. These are truths of faith, found in Scripture alone, and are properly theology.
Philosophy consists of what man can know naturally. Ideally, philosophy and theology form one system of truth; but in this life we cannot use the same method in both. Reason can, however, expose the fallacies of objections to the doctrines of faith; and faith can warn reason when it thinks it has proved a proposition contrary to faith. Furthermore, reason can demonstrate the basic proposition of faith: the existence of God.
Indeed, natural theology is the center of Thomas’ system. Augustinianism had held God’s existence to be self-evident and innate. Arguments might clarify this innate idea, but they cannot give God as a conclusion from prior first principles. Now, the difficulty with Augustinianism is its claim to grasp the purely intelligible. Man, however, is not purely spiritual; he is also corporeal; and therefore all his knowledge must begin in sensation. If one says that even so the existence of God cannot be demonstrated because it is a matter of faith alone, the answer is that as a matter of fact Aristotle completed the demonstration, and the apostle in Rom. 1:20 acknowledges the cosmological argument.
With the exception of one alteration—for Aristotle had based the eternity of the First Mover on the eternity of Motion, thus denying creation—Thomas’ proof of the existence of God is essentially the same as Aristotle’s. The first of the five forms of the argument (Summa Theologica, Part I, Q. 2, Art. 3) is briefly as follows: We see things in motion; everything in motion is put in motion by another thing (this depends on an argument involving the concepts of potentiality and actuality); a series of things in motion and movers cannot regress to infinity (if it could, there would be no first and hence no second mover); therefore we arrive at a First Mover, and this is God.
The two parentheses above, the contents of which occur in Thomas’ text, enclose two difficulties. First, the concepts of potentiality and actuality are spurious; for Aristotle, after using motion to explain them, use them to explain motion, and finally let their meaning rest on an unexplained analogy. Second, it is circular to reject infinite regress by an appeal to a First Mover in the very proof of the First Mover itself.
There is a much more profound objection to Thomas’ natural theology. Some earlier theologians, particularly those with Neo-platonic or mystical tendencies, had asserted that we cannot know what God is—we can only know what He is not. We know He is not temporal or corporeal, but the words eternal and spiritual convey no positive information. God as infinite is beyond the understanding of infinite man. Thomas, however, while granting that man can have no positive knowledge of God, allows an analogical knowledge that is superior to mere negation.
Suppose one says that God is wise. With respect to man, the term wise signifies a quality distinct both from the man’s strength, from his essence, and from his existence. But with God, essence and existence are identical, and all His attributes merge. Therefore the term wise, applied to God and man, is not a univocal term. It does not mean the same thing in the two cases.
Not only the term wise, but also the word is or exist has a different meaning when applied to God. God and man do not exist in the same sense, for with God essence is existence, and with man this is not so.
Now, the cosmological argument starts with the existence of things in motion, but its conclusion is the existence of god. It is therefore a fallacy, for every valid argument must use terms in exactly the same sense. A syllogism cannot have four terms, even if two of them are designated by the same word.
Thomas’ theory of analogy cannot escape the force of this objection. If the two instances of the term exist had some element in common, as is the case with ordinary analogies, this element would be univocally predicable of God and things. But Thomas makes it quite clear that nothing can be univocally predicable of God and things. Therefore, the cosmological argument cannot be saved.
Furthermore, analogical knowledge, supposedly superior to negative knowledge, turns out to be impossible. Analogies can be constructed only when we first know some element common to the things compared. The paddle of a canoe and the propeller of an outboard motor are analogous because in a univocal sense they are both means of a moving a boat over the water. Without this univocal purpose there would be no analogy. It is also necessary to know both the paddle and the propellor before the analogy can be stated. No one ignorant of a propeller can construct an analogy between it and a paddle, much less claim that this analogy now gives him a knowledge of the propellor which he did not previously have. It follows that we have a positive and univocal knowledge of God or no knowledge at all.
Thomism’s inability to provide positive knowledge of God derives from its basic epistemology, for Thomas, following Aristotle, held that all knowledge arises in sensation. After a man has received sensations, he preserves traces of them in the imagination; from these images concepts are abstracted, and with concepts all the propositions of intellectual knowledge are produced. Although this is a plausible theory of knowledge, it faces difficulties even aside form its theological implications.
In the first place, if sensation sometimes deceives us, and it often does, the resulting concepts are inevitably inaccurate. Aquinas was more ready that Aristotle to admit the fallibility of sense, but honest admission does not answer the objection. In the second place, neither Aristotle nor Aquinas can explain how a universal, which a concept must be, can exist in an individual, sensible object; and if it is not in the object, clearly it cannot be abstracted from it. This difficulty is bad enough when it is a case of the species “oak tree” existing in a single tree; but when the concept of the square root of minus one or the concept of the general conic is supposed to be lifted out of objects by sensation, preserved in an image, and then taken up into the intellect, the epistemological process seems to have become well nigh unintelligible.
Even convinced Thomists must admit that the universal does not exist in the thing as universal. This leads them to a distinction between the passive intellect, in which the concepts appear consciously, and an active intellect which makes the concepts, whose activity, says Aristotle, suffers no intermittence and of which therefore we are not aware.
Scholasticism has been charged with splitting hairs. There is no doubt that Thomas’ arguments are exceedingly intricate, and in no place are they more so than in his discussion of the intellect.
In conclusion and merely as a sample, there are here appended the titles of 13 articles on The Intellectual Powers, each of which Thomas discusses for two or three pages (Summa Theological, Part I, Q. 79):
1. Whether the Intellect is a Power of the Soul.
2. Whether the Intellect is a Passive Power.
3. Whether there is an Agent Intellect.
4. Whether the Agent Intellect is Something in the Soul.
5. Whether the Agent Intellect is One in All.
6. Whether Memory is in the Intellectual Part of the Soul.
7. Whether the Intellectual Memory is a Power Distinct from the Intellect.
8. Whether the Reason is Distinct from the Intellect.
9. Whether the Higher and Lower Reason are Distinct Powers.
10. Whether Intelligence is Distinct from Intellect.
11. Whether the Speculative and Practical Intellects are Distinct Powers.
12. Whether Synderesis is a Special Power of the Soul Distinct from the Others. 13. Whether Conscience is a Power.
GORDON H. CLARK