Between the second and eleventh century AD, the main philosophical influence on Christian theology was that of Plato and the Neo-Platonist tradition (as represented, by example, in Plotinus and Pseudo-Dionysius). Beginning in the twelfth century, a plethora of the works of Aristotle were reintroduced to the Western world. Although some of Aristotle’s works in logic were in available in Latin translation prior to the twelfth-century (as far back as Boethius in the sixth century), in the twelfth century a larger corpus of Aristotle’s writings (in ethics, physics, and metaphysics) were quickly becoming woven into the intellectual climate of the time. Many of these writings were translated from the original Greek into Syriac by Syrian Christians at the School of Edessa in Mesopotamia, then into Persian, and eventually into Arabic. In the twelfth century, the Aristotelian corpus was translated into Latin from both Greek originals and Arabic.

The study of Aristotle spread rapidly in the universities of Europe and by the thirteenth century became a main pillar of the medieval world view (much like biological evolution was in the 19th century). Some of Aristotle’s ideas were banned in the universities (e.g., at Paris), for varying periods of time, because they were thought to be inconsistent with Christian doctrine. Aristotle, as understood through his Islamic commentators, held that the world had no beginning in time, that there is no personal immortality, and that the supreme being is not concerned with the affairs of humans. Thomas Aquinas (1224-1274), a student of Albert the Great (an Augustinian) and avid reader of Aristotle, provides the first thorough Christian critique and assimilation of Aristotle’s philosophy into Christian theology. Two of Thomas’ main works were the summa theologiae and the summa contra gentiles.

Although Aristotle is Aquinas’ main philosophical influence, Aquinas employs some very important Platonist principles in his philosophy as well. Among these are the transcendence (and hence unknowability) of God and the existence of finite things by way of participation in the existence of God.

In both the summa contra gentiles and the summa theologiae, Thomas distinguishes between truths about God which are known by natural reason and those which are given to us by revelation, a distinction between what can be known of God "in the light of natural reason" and what is known "in the light of divine revelation." To understand this distinction we must first understand Thomas’s view of natural knowledge.

Thomas distinguishes between two kinds of natural knowledge: immediate and mediate (or inferential): what is known in itself and what is known by means of something. According to Thomas, we have certainty of the object of knowledge in both cases. The distinction here is Aristotelian in origin and relates to Thomas concept of scientia (science).

The highest form of knowledge for Aristotle is scientia (scientific knowledge). By this Aristotle means knowing some truth P, where P is logically demonstrated (or deduced) from premises which are universal and necessary and which state the cause of what is affirmed in the conclusion.

According to Aristotle, scientific knowledge is like this: we (scientifically) know a proposition P just if P is the conclusion of a logically demonstrative syllogism in which the premises state the cause of what is affirmed in the conclusion. Every branch of science (biology, physics, mathematics) can be so arranged.

In a given syllogism, the premises could be themselves logically demonstrated from some other propositions, giving us a whole chain of syllogisms. But Aristotle thought that at some point, each branch in science must have first principles which are self-evident and known immediately. These are called axioms. And like in geometry, all other propositions of a science will be logically demonstrated with reference to what is immediately known. Some of what is immediately known will be common to all sciences (e.g., logic), whereas other things will peculiar to the particular science in question and yield its unique content (e.g., biology, physics). But every science will have an axiom/theorem division. The overall structure of a scientia must be such the totality of its propositions divide into those which are as it were "ultimate premises" and those which are the conclusions. So all knowledge is not demonstrative, even if demonstrative knowledge is the highest kind of knowledge.

When we consider the contents of divine revelation, we can distinguish between:

(E.g., God exists, is one, is immutable, is good, etc.)

principle come to knowledge of without the aid of divine revelation.

(E.g, God is a trinity, Christ is God incarnate, etc)

Some of Thomas’s points regarding this distinction are as follows:

1. The distinction is not primarily or basically about WHAT is believed, but the MODE in which we know divine truth. Notice that Thomas thinks that both the preambles and articles belong to the genus of revealed truths. What differentiated them is the mode in which humans can know divine truth.

2. We can be certain of both the preambles and the articles of faith, though certainty in the case of the former is a certainty of evidentness or comprehension of what is known, whereas the certainty of faith is psychological assurance.

St. Thomas distinguishes two types of certitude (De Veritate 14.1.ad 7):

Firmness of adherence: Faith is more certain in this sense than either scientia

or intellectus. (Think of the faith of the martyrs.)

Evidentness of the object of assent: Faith is less certain in this sense than

either scientia or intellectus.

3. Although we cannot prove (i.e., logically demonstrate) that the articles of faith are true, they cannot be proven false either; therefore, any argument which purports to lead to such a conclusion must be defective (invalid or unsound). So we can demonstrate the invalidity or unsoundness of objections to the articles, but we cannot prove them true. We are open to provide evidences and probable arguments for the articles of faith (e.g., miracles), but these do not carry the force of demonstration. See article 8, question 1 (of the prima pars): Is Sacred Doctrine Argumentative?

4. Sacred doctrine is a science, specifically because it partakes of two central features of science. First, although we cannot prove that the articles of faith are true, we can use them to prove that other things are true, much like a scientist begins with first principles (which are not demonstrable in a particular branch of science) and deduced further truths. In this way, the articles of faith are similar to axioms from a methodological point of view. They constitute a starting point, from which other truths may be deduced like theorems. Secondly, although the first principles of one science are indemonstrable (in that science), they can be established by the light of another, higher science. The first principles of music, Thomas says, can be established by mathematics. Likewise, the first principles of sacred doctrine are established in the highest of all sciences, scientia Dei - the knowledge of God (God’s exhaustive knowledge if himself). And as the musician accepts a set of first principles on the authority of the mathematician, so the first principles of sacred doctrine are established on the authority of God (via the Church). See article 2, question 1 (prima pars): Is Sacred Doctrine a Science?

5. We know the preambles in the sense that they are the conclusions of logically demonstrative arguments (scientia) which take as their premises truths which are self-evident or evident to the senses. However, these demonstrations differ in one crucial way from those considered above (in Aristotle). They do not proceed from premises which state the "essence" of God, since the essence of God is unknowable to humans. A demonstrative syllogism which argues from the cause or essence of a thing is a demonstratio propter quid, an argument which proceeds by asking "what is it?." Arguments for the existence of God will be cases of demonstratio quia, which proceed from premises about effects of what is affirmed in the conclusion. The first kind of demonstration tells us why something is so; the second tells us that something is so.

Note: Thomas denies that we can have a natural knowledge of the articles of faith, but this does not entail that we can have no knowledge of them at all. One of the points to his distinction between articles of faith and preambles to the faith is to show that there are (at least) two ways of knowing divine truth. Moreover, if there is a sense of "natural knowledge" distinct from scientia, Thomas need not (and probably would not) object to the claim that we could know the articles of faith by natural reason in that sense.

1. Is it reasonable to think that there are truths about God that exceed our natural cognitive

abilities? (Chapter 3)

Yes, because human intellects are naturally limited to sense experience and God is beyond the data of sense perception, so it would be foolish for anyone to think that something is false merely because it falls outside the scope of human reason to logically demonstrate. This consideration is strengthened by comparison with everyday knowledge in which we discover that we are ignorant of many of the intelligible features of the natures of physical things which fall within the scope of human experience.

2. Wasn't it not pointless of God to reveal the preambles of the faith? (Chapter 4)

No, because (I) the arguments which establish the preambles are difficult for many to grasp, (ii) those who grasp them usually do so after spending a long time studying the arguments, and (iii) truth is mixed with error in human reasoning because of sin. But the truths about God in the preambles are very important for us to know. Our salvation and happiness depends on us knowing them.

3. Isn't it wrong of God to demand that we assent to the mysteries of the faith, given that these

mysteries cannot be rendered intellectually compelling to us? (Chapter 5)

No, since we are thereby reminded of God’s greatness and our finitude, and since these truths are not evident to us (by reason) we are allowed to embrace them freely by faith.

4. Isn't it foolish and intellectually irresponsible for us to assent to the mysteries of the faith? (Chapter 6)

No, because the articles of faith (I) are confirmed by positive empirical and moral evidences and (ii) are not inconsistent with what we know with certainty as a deliverance of reason. Arguments against the articles of faith which proceed from first principles or otherwise evident truths must thereby derive their conclusions incorrectly or invalidly, since the articles of faith are true and a valid inference from all true premises must also be true. It is also possible that such objections to the mysteries are based on false premises which are not in fact first principles of reason.

1.There can be no genuine conflict between the deliverance of faith and the deliverance of reason.

2.Apparent conflicts are in principle resolvable by us

3.Philosophical or scientific objections to the faith can and should be answered on their own terms--this is an important task for Christian intellectuals.

4.Reason, while not so corrupted by sin that on its own it yields falsehoods as certitudes, nonetheless needs the guidance of faith to do its best.

5.Philosophical reason is an important tool in spreading and maintaining the faith.

III. Getting to God: Arguments for the Existence of God (SCG, chapters 10-13) 

1. The existence of God is self-evident

It is sometimes argued as follows:

There are some propositions that are known immediately upon grasping the meaning of their terms. Such is the as we with "the whole is greater than its parts." The proposition "God exists" is like this. A person who hears and understands the name "God" has in his mind a notion of "something than which a greater cannot be thought." So "God" exists at least in the intellect. But if he did not also exist in reality, he could not even exist in the intellect, for that which exists in reality and in the intellect is greater than that which exists in the intellect alone. But what is in the intellect is something than which a greater cannot be conceived. Nothing can be greater than what a person has in mind when they think "God", so God exists is self-evident from the very definition of God.

Thomas does not mention St. Anselm here but he is thinking of Anselm’s famous ontological argument that follows the same pattern.

But, Thomas thinks that:

(i) Some things are self evident in themselves, and others are self-evident to us (humans). It is self-evident to us that "the whole is greater than the part" because we know the essence of a whole. It is self-evident in itself that God exists, since God’s existence is his essence and conversely. But we do not known God’s essence, so it is not self-evident to us that God exists. (ii) The existence of God is not known from knowing the meaning of the name "God," since (a) not all understand by "God" that than which a greater cannot be thought" and (b) even if one did understand "God" to mean "something than which none greater can be thought" it would not follow that such a being actually exists, since one can understand the concept of a thing without positing that it has been instantiated.

2. The existence of God is held by faith alone

It might be argued:

For various reasons some have doubted that the existence of God can be demonstrated and therefore that it must be held by faith alone. Following Aristotle’s notion of demonstration, it might be thought that all demonstration requires a knowledge of the essence of a thing, and therefore, since God’s essence is unknowable, his existence cannot be demonstrated. Secondly, since the knowledge of the principles of demonstration derive from sense experience, whatever transcends sense experience is indemonstrable. Since God is beyond all sense experience, so nothing can be demonstrated of him.

Thomas says:

Based on Aristotle and Scripture we know that there is a second kind of demonstration which proceeds from effects to cause, and so does not require a knowledge of the essence of the thing one is trying to prove something about. Such an argument, demonstratio quia, does not take the essence of a thing as the middle term, but rather an effect is taken as the middle term. And from such effects, the meaning of the name "God" is arrived at. Moreover, since effects resemble their causes, God’s transcending sense experience is not barrier to our reasoning from the latter to the former.

(P1) Some things are in motion.

(P2) Everything that is moved is moved by something else.

(P3) It is not possible for there to be an infinite series of movers.

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(C1) Therefore, there is some unmoved mover that we call God (deus).

(P1) Clarified: to be in motion is undergo a change, locomotion (a kind of accidental change). In other terms, following Aristotle, when X is moved there is an actualization of some potentiality, or a reduction of potentiality to act.

1. Aquinas proves (P2):

(P4) Everything that is moved is, as moved, in potency.

(P5) Everything which moves is, as mover, in act.

(P6) Nothing can be in both potency and act with respect to the same motion.

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Therefore, (P2) Everything which is moved is moved by something else.

[Two other proofs are given]

2. Aquinas proves (P3):

(P7) If there is an infinite chain of movers, then each member would be an intermediary cause.

(P8) If every mover is an intermediate cause, then there is no principal cause.

(P9) There is no intermediary cause without a principal cause.

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Therefore, (P3) It is not possible for there to be an infinite series of movers.

In addition to the Five Ways (argument from motion being the First Way), there is in Thomas an argument from the act of existence or existing which leads to the conclusion that there is a God. Bearing in mind that by "explanation" we mean "causal" explanation, the following seems to be the case:

(1) There are things that exist.

(2) An existing thing X is not identical its essence.

(3) The essence of a thing X does not explain X’s existence (since you cannot deduce the existence of a thing from its essence)

(4) The existence of a thing X does not explain X’s existence (since X would already have to exist to provide an explanation of its own existence and that would mean that X preexists itself).

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(5) Therefore, the explanation of a thing’s existence must be something external to the thing.

(6) For any existing thing X, there cannot be an infinite series of external causes of X’s existence.

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(7) There must be one external cause of existence for every existing thing.

As in the argument from motion, (6) may be arrived at by a reductio ad absurdum: If each cause of X’s existence were itself in need of a cause of its existence, then no cause of A could exist, and A itself could not exist. But A does exist. So there must be a finite chain of causal explanation for the existence of things which terminates with a being whose nature or essence it is to exist, and this everyone understands to be God.

1. All begin with what is evident to the senses (empirical starting points).

2. Nearly all rest on the absurdity of an infinite regression.

3. All assume a point of termination with Deus (God).

In the fashion of Aristotle, Thomas distinguishes between questions an sit (whether something exists) and quid sit (what it is that exists). Having shown that there exists a first being, whom he calls God, he must now investigate the properties of such this first existent. 

1. Anthropomorphism: The position according to which God is a being who has

perfections proportionate to those of creatures, only to a much higher degree

2. Obscurantism: The position according to which God is so utterly different from

creatures that none of the perfections belonging to creatures in any way resembles any

perfection belonging to God

Two Crucial Limitations on our Knowledge of God:

1. All knowledge is rooted in sensory perceptual experience. But God, being immaterial and invisible, is not an object of sensory experience

2. All "strictly" scientific knowledge of a thing requires a logical demonstration from the essence of the thing and the classification of a thing in terms of genus and species. But we do not know the essence of God and so we cannot locate God as a member of any genus. In fact, God IS NOT a member of any class of things.

In the summa theologiae, Thomas says: "We cannot know what God is, but only what he is not." That statement must be understood in terms of the above two constraints. It does not mean that we can make no true statements about God or hold no true beliefs about God. We have no positive quidditative or natural-kind concept of God (also called negative theology or via negativa).

Therefore, we must first ask not what God is but what he is not. God lacks various kinds of COMPOSITION which characterize finite creatures and characterize them essentially. God is not a composition of spatial or temporal parts (and so is immaterial and timeless). God is not a composition of actuality and potentiality (and so is wholly immutable). Think of Plato’s forms. God is not a composition of what-ness (essence) and that-ness (existence). He is his own act of existence. He is not a composition whatness (essence) and individuality (suppositum).

Since the argument from motion assumes that effects resemble their causes, there must be some similarity between God and the created order. The first case of this is that the "existence" of the world points to a supreme act of existence. But we know that if a supreme act of existence is to explain all cases of limited acts of existence, then certain things cannot be true of the supreme act of existence. Nothing can be true of this being which allows us to ask "Who made God?" or something like that. The principle of divine simplicity provides constraints on how we are to think about God. Therefore, if we affirm anything positively about God, it must be subject to this restriction. But we do have such positive affirmations about God (that God is good, wise, etc.). These are not intelligible as mere negations, nor are they metaphors, so they must be predicated literally of God but ANALOGICALLY.

1. Types of literal predication:

Univocal: Same name and same kind of form: 'Socrates is wise' and 'Plato is

wise'

Equivocal: Same name but utterly disparate forms: 'Babe's bat weighs 37

ounces' and 'A bat is a mammal'

Analogical: Same name and different but ordered forms: 'This animal is

healthy' and 'This food is healthy'

As applied to God: 'Socrates is wise' --- 'God is wise' --- 'God is Wisdom'

2. Names that are literally predicated of God:

Those that signify pure perfections: 'wise', 'good', 'intelligent',

'provident', 'merciful', 'just', etc.

Those that signify preeminence in perfection: 'First Efficient Cause',

'Unmoved Mover', 'Unlimited (Unparticipated) Being', 'Pure Actuality',

etc.

3. Names that are metaphorically predicated of God:

Those that signify a perfection but express a mode that can belong

only to a creature: 'rock', 'mighty fortress', 'lion', 'paper towel'.

In short, the doctrine of analogy is based on the positive affirmation that there is a First Cause. (1) Since effects resemble their causes, perfections found in the created order are found supremely in God. (2) Since the first cause must be wholly simple, all perfections found both in the created order and in God will be possessed by God in a mode different from their possession by finite creatures, i.e., God holds every perfection in a wholly simple manner.

Where X is some perfection, X is predicated analogically of God and finite creatures means:

X, the perfection signified (res significata), is the same for God and finite creatures. The mode in which X is possessed (modus significandi) by God and finite creatures is not the same.

X is true in a wholly simple manner with God.

X is true in a composite manner with finite creatures.

(E.g., while, John is good, God is goodness itself).

© Michael Sudduth 1997