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 that are known by natural reason and those that are given to us by revelation. This is 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 that 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 that 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:

Preambles of the faith: those revealed truths that natural reason can in principle come to knowledge (scientia) of without the aid of divine revelation. (E.g., God exists, is one, is immutable, is good, etc.)

Mysteries of the faith: those revealed truths that natural reason cannot even in 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.

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.

Structure of the Summa Questions:

ARTICLE: is it the case that?

OBJECTION(S): it seems that (usually a negative answer to article question) [videtur]

ON THE CONTRARY: Thomas answers the objections. [sed contra]

I ANSWER THAT: Thomas develops the answer to the objections. [respondeo]

Whether, Besides the Philosophical Sciences, any Further Doctrine is Required?

a. The philosophical sciences deal exclusively with what can be known by reason. But we should not seek what is beyond reason. Therefore, there is no need for any doctrine beyond what is contained within the philosophical sciences.

b. Knowledge is concerned with what is (being). All that is (being) is contained within the scope of the philosophical sciences. Therefore, there is no need for anything beyond the philosophical sciences.

General

Humankind is directed toward God. Therefore, the human person has an end (telos) which surpasses the scope of human reason. For the sake of human salvation it was necessary that God reveal by means of a divine revelation (a) truths which are beyond the grasp of human reason and (b) truths which are within the reach of human reason. (a) because otherwise such truths could not be known at all. (b) because man's natural knowledge of divine things is sometimes tainted with error and known only after long time of study and then only to those with intellects keen enough to grasp philosophical arguments. Aquinas says essentially the same thing in the Summa contra Gentiles, 1.4.1-7 (cf. 1.5.1-5)

a. We should not seek by reason what is beyond reason. But we must accept what is beyond reason by faith.

b. We distinguish one science from another by the mode in which they know some truth. So the same divine truth can be an object of knowledge according to the light of natural reason and according to the light of natural reason.

3. Preambles and Article of Faith

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

Whether Sacred Doctrine is a Science?

a. Every science proceeds from self-evident principles. Sacred doctrine proceeds from articles of faith, but the articles of faith are not self-evident (they are not admitted by all). Therefore, sacred doctrine is not a science.

b. No science is concerned with individuals. But sacred doctrine is concerned with individuals (e.g., Abraham, Moses, and St. Paul). Therefore, sacred doctrine cannot be a science.

All sciences proceeds from principles which are known by light (quae precedunt ex principiis notis lumine). There are two kinds of sciences. Some sciences take as their principles what is known by the light of natural reason (quae procedunt ex principiis notis lumine naturali intellectus); other sciences take as their premises principles which are deductions from higher sciences (quae procedunt ex principiis notis lumine superioris scientiae). The former sciences are called "subalternating sciences." The latter sciences are called "subalternate sciences." So what is a theorem in a science which has self-evident principles as its axioms can become an axiom for some other science. Sacred doctrine proceeds from a higher science - the science of God - in this manner.

a. The principles of any science are either evident in themselves or made evident by the light of another science. The latter is the case with sacred doctrine.

b. The individual facts treated by sacred doctrine are not treated principally as individual facts, but as examples of general truths which we must follow and to establish the authority of the men through whom divine revelation has come to us.

Whether Sacred Doctrine is Argumentative?

a. Arguments and faith are mutually exclusive. But sacred doctrine is aimed at faith. Therefore, sacred doctrine is not argumentative.

b. Arguments are either from authority or reason. If from authority, then the process would not be appropriate for the character of sacred doctrine, for argument from authority is the weakest kind of argument. If from reason, then the process would not be appropriate for the purpose of sacred doctrine, for faith has no merit where reason has proof from experience.

Sacred doctrine, like every science, does not argue to its premises, but argues from them to other establish other truths. Subordinate sciences do not attempt to prove their first principles nor argue with those who deny them. Although reason cannot prove (the truth of) the articles of faith, it can prove the invalidity of arguments against the articles of faith. The articles of faith are true, and the contrary of truth cannot be logically demonstrated. Aquinas develops these points also in the Summa contra Gentiles, 1.7.1-7.

a. Sacred doctrine does infer other things from the articles of faith.

b. Argument from authority is strongest when based on God’s word (though weakest when based on human testimony).

If sacred doctrine were logically demonstrated it would destroy the merit of faith, for we have no choice in assenting to what is evident to us. But, grace perfects nature, so there is a place for natural reason vis-a-vis sacred doctrine. So we may use the philosophers where they have perceived the truth by reasoning. But philosophical and ecclesiastical authorities provide only probable arguments, whereas those based on Scripture have convincing force. See also Summa contra Gentiles 1.7.6-7.

It is self-evident that there is God? (utrum deum esse sit per se notum)

Can it be made evident? (utrum sit demonstrabile)

Is there a God? (an deus sit)

1. Videtur

a. Whatever we are innately aware of is self-evident. That there is a God is something we are innately aware of. Therefore, it seems it self-evident that God exists.

b. If we perceive the truth of a proposition immediately upon understanding its terms, then the proposition is self-evident. Since God is "that than which nothing greater can be signified" and since "existence in thought and fact is greatewr than existence in thought alone," we immediately apprehend that God exists from what we understand from the word God. Therefore, it is self-evident that there is God.

General

But nobody can think the opposite of a self-evident proposition, but the opposite of God exists can be thought, for the fool has said "There is no God." Therefore it is not self-evident that there is a God.

Thomas distinguishes between a proposition's being self- evident in itself (per se nota) and being self-evident to us (per se nota nobis). Some propositions are self-evident to us, since we know the meaning of the terms: a whole is greater than its parts. First principles of demonstration are self-evident to us when their meaning is grasped by everyone. But some propositions have terms which are not understood by all, even though the predicate forms a part of the subject (or is contained in the subject). Now <God exists> is self evident in itself, since the subject and predicate are identical. But we do not know the essence of God, so it is not self-evident to us. It must therefore be made evident to us by things that are more evident to us to begin with, namely God's effects.

a. The awareness of God implanted in us by nature is a general and not altogether perspicuous awareness. It is similar to the difference between the awareness that "someone" is approaching and "Jeff is approaching."

b. Some people who hear the word "God" do not understand by it "that than which none greater can be thought." Some have thought that God is a body. And even if people understood "God" to be mean "that than which none greater can be thought" there would still remain the question of whether they understood it to actually exist (whether they understood that the concept had an instantiation).

1. Videtur

a. It seems that God's existence cannot be demonstrated, for it is an article of faith, for as Paul says, faith is concerned with what is unseen, what cannot be demonstrated, that is - made evident.

b. Essential to demonstration is definition, but God - as Damascene points out, cannot be defined. Therefore, we cannot make God's existence evident.

c. God's existence could only be made evident by his effects, but since God is an infinite cause and his effects finite, there is an incommensurability between them. Since, effects incommensurate with their cause cannot make their cause evident, the possibility of a logical demonstration of God's existence from his effects is precluded.

a. General

St. Paul tells us that "the hidden things of God can be clearly understood from the things that he has made." Therefore, it must be possible to demonstrate that God exists.

There are two kinds of demonstration.

One that shows WHY something is, which argues from cause to effect (or from a things essential nature to its properties). Such an argument proves its conclusion by a premise which is the definition of a thing. (demonstratio propter quid)

Here premises (1) and (2) contain a term which is the definition of the subject of which something is predicated in the conclusion.

One that shows THAT something is, which argues from effects to cause and which proves its conclusion by a premise that states the effect of a thing. (demonstratio quia)

When effects of a thing are better known to us than the cause, we must demonstrate the cause from its effects. Since effects are dependent upon their causes, we can provide such a demonstration.

a. The truths that we can know by natural reason (stated by St. Paul) are not to be numbered among the articles of faith, but are presupposed by them. Since there is nothing to stop a person from taking anything on faith which he cannot personally demonstrate, it is permissible to take the existence of God on faith even if it is the sort of proposition which can be demonstrated by human reason.

b. In a demonstration from effects, an "effect" (of some cause) takes the place of the definition of the cause. And when we are proving that something exists, the central link in the proof is not WHAT a thing is, for we must first know THAT it is before we ask WHAT it is. In proving that God exists from his effects, we will derive the names of God from his effects.

c. An effect will give comprehensive knowledge of its cause when it is commensurable with it, but even with such commensurabilty does not exist, we can at least pass from an effect of x to the conclusion that there is an x, though we cannot know comprehensively WHAT x is. Such is the case with God.

1. Five Ways are NOT necessary for a person to have a rational belief in God.

The person need not himself work such proofs in order to have a rational belief that there is a God, though Thomas MAY think that the rationality of theistic belief in someway depends on the availability of such proofs in one's community (Anthony Kenny's interpretation), though this may depend on what sense one gives to "rationality."

2. Five Ways DO provide material for a project such as apologetics, even if that was not what motivated Thomas himself to develop these proofs.

3. Five Ways ARE part of a scientia theologiae, a science of theology, in which what CAN be known by reason

1. empirical starting points [certum est]

It the world we find that there is change, an order of efficient causes, contingency, things which are more or less

perfect, and things without cognition work toward an end). These are all supposed to be obvious

2. The existence of what is observed in the first premise (starting point) implies the existence of something else. [omne quod movetur ab alio movetur]

3. Impossibility of an infinite regress [ad infinitum]

4. There is some first term existent

5. All five ways conclude that there is a legitimate name for this first term existent: Deus

(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.

=============================================

(C1) Therefore, there is some unmoved mover

=============================================

(C2) Everyone understands this being to be God (deus).

(P1) Clarified: to be in motion is to 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 that moves is, as mover, in act.

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

==========================================

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

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.

=======================================

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

*****