General Notes on Thomas Aquinas

I. Philosophy and Theology in Thomas' Thought

A. Philosophy as ancilla theologiae.

Aquinas was first and foremost a theologian, though he was quite capable of distinguishing philosophy proper from theology. He stated that (i) philosophy can prove by means of reason unaided by revelation some truths proposed by Christian faith; (ii) it can clarify truths which cannot be proved; and (iii) it can defend the principles of Christian faith against their detractors.

True philosophy cannot conflict with Christian faith but it can fall short of it e.g., the existence of God as efficient cause of the universe can be established by reason alone, the full meaning of "God" can only come from faith.

Aquinas is the greatest of those medieval thinkers who tried to incorporate as much of Aristotle's ideas as possible into Christian philosophy. He goes as far towards accepting Aristotle's views as it was possible for a Christian of his time to do. But there are some points regarding which it would virtually impossible for a Christian not to depart from Aristotle: chief among them (i) his insistence on the eternity of the world and (ii) his rejection of individual immortality.

B. Christian PHILOSOPHY

Philosophy as Thomas understands it depends on this: that there is a natural world; that its substantial components regularly exercise their own causal powers; that there are intelligent beings capable of understanding the natural world by their own mental powers.

C. CHRISTIAN philosophy

Christian philosophy for Thomas depends on this: that the world of creatures is totally based for its existence, endurance and operation upon God, who freely creates, conserves and cooperates with what He has created.

A. What X is (X's essence), and That X is (X's existence).

A key feature of Thomas' philosophy is his account of essence and existence. We can distinguish in any finite being what it is, its essence, and the fact that it is, its existence. Avicenna had treated the existence of something as an accident, imposed on it from without by an external cause.

Thomas says that in each thing there is a nature or essence which is actualized by the ultimate reality or act of being. His point is that we can understand an essence without our knowing whether there are any examples of it in the universe. I can know what a peregrine falcon would be without knowing whether there are any peregrine falcons in the universe.

B. Essence as Potentiality, Existence (esse) as Actuality.

Being is the actuality of every form or nature. For Thomas, an essence is a potentiality whose actuality is the act of existing. In the case of finite beings, of creatures, the act of existence is received from God.

C. How this relates to Aristotle's view of substantial form as actuality.

We should note what has happened here to Aristotle's association of essence with soul, and soul with actuality. From the perspective of Aristotle's philosophy of nature, the study of natural things including living beings, the soul is the actuality of a body which is potentially alive. From the theological perspective of Thomas, thinking of a God who creates creatures freely, the essence of something is insufficient to guarantee its existence God's free creation is still required. With respect to God, who need not have created this individual, the individual, her soul included, is a potentiality, a possibility.

God Himself is absolutely simple. An essence in God is nothing more than God's knowledge of one way His divine nature might be imitated in the created world.

D. Thomas' individuated hylomorphic conception of essence

We need to be clear how the notion of essence functions in Thomas. For Aristotle, there seems sometimes to be an equation between formal cause and essence. Now, the same Greek word is translated into Latin as forma (form) and species (species). This is possible because we identify species most often by their common form or nature. Now, besides a shared specific form, we can also speak of an individual form, Socrates' human form, which is the same in definition as Plato's or Aristotle's, but for the fact that it is one person's form rather than another's.

Now, the issue is more complicated still, because the essence of a living being is not exhausted by its form, its soul; a corporeal being must have matter or a body appropriate to house or receive its form. Thus, one may speak of an essence as including both form and matter. Moreover, this composite essence may be individuated or conspecific. My essence includes my human form and my material body which receives this form. The human essence may be the essence of humans as involving a form or soul of a definable type and a body of a definable type.

* form (e.g., human) shared by individual and other members of its species
* individual (e.g., Socrates' human) form but "formally" or specifically identical to forms of others in its species
* form (e.g., human) shared by members of same species and generalized matter (appropriate to this shared form)
* individual (e.g., Socrates' human) form and matter (appropriate to this form) both specifically identical with form and matter in other members of its species.

When Thomas thinks of essences or natures of created living things, he tends to think of individual living things, each with an individual soul or form and a body or matter to go along with it. The essence of angels is form alone, for angels are purely spiritual or intellectual substances; they are free from matter and do not need it.

E. That which is (essence), and that by which it is (existence).

Thomas distinguishes, then, the essence, that which is, from the act of being, that by which it is. Angels exist because their essences or forms were given being by the divine act of being.

F. Double composition of corporeal creatures:([m+f] + aob).

Composite creatures, like ourselves and plants and animals, exist because their matter form essences were given being. Thus we exist as what we are thanks to a double composition, [(form plus matter) plus the act of being.]

Aquinas sets forth five ways in which God's existence can be proven. They all (1) start out from sensible events or facts; (2) they all contain some sort of principle of causality.

Three of them possess a premise that rule out an infinite series of causes.

Feature (1) makes the five ways a posteriori arguments, based on experience. Aquinas rejected attempts to prove God's existence a priori, on the basis of our concepts (esp. of God) alone. (Anselm before him and Descartes and Leibniz after him attempt to construct such a priori arguments.)

One of Aquinas' five ways is Aristotle's argument that there must be an unmoved mover:

If B moves A, then A must go from potency to act and B must be in act.
But if B owes its motion to anything else, then it must have a mover C; and so on.
An infinite series of in themselves potential movers is impossible (for then no motion would occur).
Hence there must be an unmoved mover.

Each of the "Five Ways" arguments is meant to establish the existence of some feature of God: unmoved mover, ultimate cause for all change, necessary being, most perfect being, intelligent director of the universe.

Two types of "analogy."

Aquinas denies that the mind possesses any innate ideas; what we know is based upon sense experience. But the mind can mount up from ideas based directly upon sense experience to ideas of immaterial beings and even of God. Terms applied to God will be taken from terms applied to creatures, but their meaning will not be the same in both cases.

Identity or sameness of meaning exists when two things called by the same name belong to the same species or genus. But God does not belong to a species or genus with anything He has created. Aquinas says we can speak of God only by analogy.

He distinguishes two types of analogy, analogy of proportionality and analogy of proportion. Analogy of proportionality has roughly the form of mathematical proportions:

a:b :: c:d

e.g., divine goodness is to human goodness as God is to man.

Analogy of proportion, by contrast, dispenses with the quasimathematical formulation. It seems to mean that the terms applied to creatures can be applied to God because God is the cause of the perfection of the creatures and because the aspect of the creatures from which the term applied to God is taken exists in God in a higher degree. (Weinberg, 193). Thus God may be called good by analogy of proportion because God's goodness is a cause of human goodness (when and to the extent that it exists) and because the goodness found in humans exists in God to a higher degree.

A. Creation and Prime Matter

The creation of everything in the world must be attributed to God, including prime (unformed) matter, though Aquinas remains close to Aristotle when he holds that matter can exist only with some distinct form or other. If prime matter existed by itself, that would imply that pure potentiality existed by itself, a contradiction in Aristotelian terms. Thomas thus rejects the notion that matter has independent reality of its own. (Duns Scotus and William of Ockham were later to hold the view Thomas and Aristotle rejected).

B. The Beginning of the World: Not Provable

Did the world have a beginning in time? Aristotle held that it did not. But his reasoning was only aimed at refuting erroneous views about the beginnings of things. So, Thomas holds, philosophy does not require that we accept the view that the universe is eternal. But no one has supplied a sound philosophical argument that the universe did have a beginning in time. (Bonaventure had thought he had a sound argument, but according to Aquinas he did not.) It is logically possible that there has been an infinite number of creatures in a temporal series. The newness of the world as revealed by Scripture, the doctrine that there was a first moment of time, must therefore be accepted upon faith. It cannot receive a grounding from philosophy.

Aquinas is not being inconsistent when he holds that an infinite temporal series is possible while denying, in his proofs for God's existence, that an infinite series of moving causes is impossible. We must distinguish between a series on the same ontological level, which is what we have in mind when we are dealing with temporally successive events, and a series in which the cause is always ontologically superior to its effect.

C. Aquinas vs. Hume on causation.

We are accustomed, since David Hume in the 18th century, to think of cause and effect as two distinct events, the first of which just precedes the second in time. Such events are metaphysically at the same level, one is just as real or basic as the other. But there is another, probably older, conception of cause (which goes all the way back at least to Plato): the total cause is more real than the effect. This notion of cause is not found only in philosophy but in ordinary thinking too. What prevents the roof from caving in onto the floor and crushing us? The rigid bodies in the walls of this room. These rigid bodies support the position of the roof because they are physically more powerful than the weight of the roof. Moreover, rather than working earlier in time relative to the roof's being apart from the floor, these rigid bodies operate at the same time as the roof-floor gap. Now, what Thomas takes as self-evident is that there is no infinite series of causes understood in the second way, as support causes. In other words, if there is anything at all, there must be an ontological maximum.

God, whose gift of acts of being is the ultimate support cause, creates his creatures simultaneously with their existence. As Augustine already realized, there is no need to speak of God the creator as existing in a time prior to the existence of the creation.

God created a many tiered ontological hierarchy of beings because one or a few tiers would not exhibit his perfection adequately. There is one mundus (universe), organized by three types of finality or purposiveness: (i) the parts of any creature exist for the sake of the creature; (ii) creatures at one level exist for the sake of creatures at higher levels (as plants for animals, and at least some animals for human beings) and (iii) the whole universe is ordered to God, the end and the good of the whole creation.

There are bodiless intelligences inferior to God, i.e., angels. This is why: God must be imitated as much as is possible in creation (for creation is God's chief expression). Nothing can duplicate God, but there can be creatures who act much like God even thought they are not absolutely perfect. God acts by intellect and will he does not use corporeal instruments. The angels, bodiless intelligences (matterless forms) act in the same way.

Ibn Gabirol had argued that angels must be a union of form and spiritual matter that would be one way of distinguishing them as less perfect than God. Thomas rejects this solution: Angels are distinguished from God by the fact that there is a distinction in them between essence and existence, while there is no such distinction for God.

There is also a distinction in corporeal creatures between essence and existence. This is the most pervasive form of composition for Thomas; matter form composition is limited to corporeal creatures.

A. The doctrine of the plurality of substantial forms

For Aristotle, a living being's soul is its substantial form. But souls have distinguishable powers, such as nutrition and growth, sensation, and rational thought. And since psychological powers are attributed to bodies as predicates are attributed subjects, the problem arises whether there might not be several substantial forms in a single body. The living human being might contain at least three one for nutrition, one for sensation, one for reason. This approach might be tempting for Christians, because one could then explain the difference between the resurrected person and the ordinary living person by saying that the nutritive form is absent in the resurrected person.

B. Aquinas' rejection of this doctrine

Thomas rejects this multiplication of substantial forms. A living creature has at most one substantial form. The primary reason for this is that animals and especially human beings are units, they possess unity in a very strong sense of the term. This could not be the case if each of us had distinct substantial forms. (Remember, however, that the human essence is both form and matter.) Human souls, for Thomas, qualitatively differ from animal souls in that human souls alone are capable of existence independent of the body.

C. The double orientation of the human soul

Thus for Thomas human souls face two directions as substantial forms of their respective bodies, they bring actualize life in the body. But as incorruptible souls, they are prepared for existence outside of the body.

Though creatures have only one soul, some of them, including human souls, have several capacities or powers. There are five classes of powers of soul in human beings:

a) vegetative
b) sensitive
    i) functions of exterior senses
    ii) functions of interior senses
        a') common sense
        b') phantasy
        c') imagination
        d') estimative
        e') memory
c) appetitive
d) locomotive
e) intellectual

A. Agent, Possible and Passive

Each human intellect (intellectual power of soul) contains active (agent) intellect, possible intellect and passive intellect. Here, as often elsewhere, Aquinas consciously and directly rejects a position of Averroes. Averroes had held that the passive intellect was merely an imaginative power and that the active and possible intellects, which belonged to the intelligence that governs the sublunary world, operated on human beings from outside themselves.

B. Self evident Judgments, Inference

Human thought operates in the following way:

1. Simple apprehension grasps the indivisible forms of being, i.e., substances, qualities, relations, etc.

2. Affirmative and negative judgments compound and divide. (To affirm is to put together two forms, to negate is to separate them.)

3. Inference proceeds from what is known to what is not known.

For Aquinas the mind does not err in apprehension of essences: it either has a simple concept or it does not.

Moreover, some propositions are knowable with certainty: self evident principles, for example, are known without error once we understand the meaning of the terms. (Similar to analytic judgments in Kant or analytic propositions in 20th century positivism.)

C. How the Mind Comes to Know Universals

The mind acquires simple concepts thus:

1) external objects produce duplicates of their sensible forms in the medium between the object and the sense organ;
2) these sensible forms are communicated to the sense organs;
3) these sensible forms are communicated to the faculty of sense;
4) these forms in the sense faculties are brought together by the internal senses into a common image or phantasm;
5) active intellect abstracts the intelligible form from the image;
6) the intelligible form is retained in possible intellect for reactivation at will for future active understanding.

A. The problem: Are Universals one or many?

How does Thomas resolve the problem of universals bequeathed to the Middle Ages by Boethius' commentary on Porphyry's Isagoge? The problem involved whether the nature of a thing is one or many. Thomas said that the nature of a definite thing is neither one nor many. Humanity, the nature of humans, or whiteness, the nature of white things, considered as such, is neither one nor many.

B. Solution: Universals as such are neither.

His logic is this: If humanity were simply one, then there would be no more than one human being; and if it were simply many, then it would be impossible for us to understand something about many human beings by understanding the one common nature. Humanity as such is indifferent to being one or to being multiplied in many individuals. The universal may be considered, of course, either as it occurs in individuals, in which case it is many, or as it occurs in the mind, following abstraction; only when it exists in the mind does it have the character of the universal or concept. When it does it can be attributed to a number of individuals existing in the external world.

C. Specific sameness of the common nature in individuals.

The nature of all individuals of the same species is one in the sense of specific sameness or identity. There is not a single thing, e.g., a subsisting Platonic form, which is there common nature. Rather humanity in me and in Gandhi and in Napoleon is a total similarity of the human form in me, the human form in Gandhi, the human form in Napoleon.

D. The role of designated matter.

What differentiates one human being from another is its designated matter (materia designata), matter existing in certain dimensions, place and time. Without such matter, there could be only one form per species. Hence intelligences or spiritual creatures, i.e., angels or demons, which possess no designated matter, have specifically different essences.

If we were to say that the mind strictly understands such universals by themselves, we would be laying the basis for a logical error. For it would then be possible that we might judge the form of humanity to subsist independent of individuals, that is, to exist as a single form other than as a concept in individual minds. This conclusion, which in any case does not follow from Thomas' account of abstraction, is rejected by Thomas.

If learning by way of abstraction could lead to this conclusion, abstraction would be a deceptive process. The key is to get our terms straight. We do not really understand or know universals as such. We understand or know by means of universals. In understanding a material object, the intellect must turn towards the phantasm (image) of the object; thus, by means of its awareness of the phantasm, it recognizes that it is perceiving a single thing (the external source of the phantasm).

According to Aquinas, we understand more generic features of embodied individuals before we understand them specifically; thus we understand humans and horses first as living things, then as sentient things or animals, and then only as a specific type of animal. Our grasp of concepts arises from the individual, i.e., from sense experience of individual things. Moreover, our understanding always refers back to the individual. In that sense, the individual is prior to the universal. But what we learn about individuals first is their more general attributes.

We also are able to know two classes of incorporeal beings. Human souls are known by reflection upon our own acts of knowing. The existence of angels, demons and God are known by inference from our knowledge of material things. According to Aquinas, these things are known very indirectly and imperfectly in this life. This humility did not prevent him from reasoning and publishing at great length about these topics.