The Feast of St. Thomas

Today, 28 January, is the Feast of St. Thomas Aquinas, translated. Do something logical in his honor.

His feast had been set originally on 7 March, the day of his death, as is customary. But it fell within Lent too often and so was shifted in 1969 to 28 January, when his remains were removed from Naples, where he had lived, and reburied in the Church of the Jacobins, the mother church of the Dominican order. This process is known as "translation." During the Revolution, the church was vandalized by the Enlightened: the stained glass windows were smashed and the medieval murals painted over with whitewash. The building was converted into an army barracks. In the early 20th century, the building was restored bit by bit and functions now as a monument and museum. It was called the Church of the Jacobins not because the leftist armies had vandalized and occupied it, but because the Dominicans had once been headquartered in Paris on the Rue St.-Jacques.

To celebrate the day, TOF will try briefly to recap one of his famous metaphysical demonstrations in as modern a lingo as possible; to wit, the Argument from Motion.¹


Motion (kinesis in Greek) meant a reduction of potency to act; that is, from potential being to actual being. For example, an apple that is actually green is potentially red. So "ripening" is a form of motion. Other examples of motion include: the firing of neurons in the brain, the formation of compounds in chemistry, and the fall of an apple onto Newton's head. In the present day, 'motion' is used more often to refer to a movement of location (local motion). The apple is actually here on the tree, but is potentially there on Newton's noggin. To incorporate the larger sense, let's say "change" instead of "motion."

1. "It is certain, and evident to our senses that some things in the world are changing." Hard to argue with that; although there are those who, knowing where this is all leading, will stand with Parmenides and declare that all change is an illusion. [What they plan to do with physics and chemistry afterward, let alone biology, is a mystery.] 

The soul [form] of anthocyanin

2. "Whatever is changing is being changed by another." Something that is not actual can't do diddly squat. But a thing cannot be both potentially X and actually X in the same respect at the same time. An apple cannot be potentially red and actually red at the same time. Therefore a thing cannot change itself; that is, it cannot be its own changer. Something already actual must cause the change.  The apple does not redden itself. A green apple is made actually red by the action of sunlight in the 3,600 to 4,500 Å range, which causes the anthocyanin in the skin to absorb the near-ultraviolet, violet, blue and green regions of the spectrum, thus reflecting red. The sunlight is actually red -- check its spectrum for details -- in the eminent sense.

An inanimate body in rectilinear motion cannot change its velocity or direction by itself. A change in velocity is an "acceleration," so this dictum of Aquinas is simply Newton's First Law, generalized.


So the "changer" may be sunlight, a gravitational field, a collision with another body, or something else of that sort. In the case of animate beings, the changer may be a proper part of the whole. The cat crosses across the room because it is being moved by its legs. (And the legs by the muscles, and the muscles by the nerves, etc.) 

3. Before anything that is “by another” there must be something “not by another.” If C is being changed by B, then the same applies to B: it is being changed by another as well. Let's say A. This cannot go on indefinitely, because if it did there would be no first changer. And if there were no first changer, none of the subsequent changers would have the power to reduce a potential to actuality and there would be no change in the world, a contradiction. 

For example, an actually dry towel is potentially wet. But it is not wet simply because it is a towel. That is, the towel is not wet "by itself." Therefore, it must be wet "by another," such as the water in it. But this does not go on without limit. When we ask what made the water wet, we realize that water is wet by itself, not by something else.

The answer to what makes water wet is "strong tetrahedral hydrogen bonding," but notice that this is a formal cause, that is, an emergent property. It is something that stems from the form of water itself. A formal cause is that which makes a thing what-it-is. As such, it is not a potential being reduced to actuality, but is the actuality of water itself. 

What is actualized "not by another" can be of two kinds. That which is actually X "by itself" -- i.e., formally -- and what is not X at all. That is, something of another order. Suppose a chain email letter is forwarded to you, and you forward it to someone else and so forth. You are a "sent sender." But there is nothing in the nature of forwarding that accounts for the existence of the email, its "coming-to-be." There must be an "unsent sender" that accounts for the content of the email. But composition is of a different order than the forwarding, even if the sequence of sent senders were infinite. It is only infinite in time sequence. In ontological sequence, there is an unsent sender, or First Sender, the composer, and then there are forwarders. The First Sender need not be the first in the temporal sequence, and often is not.

Another example: imagine an intricate set of dominoes toppling one into another. The first mover is not the first domino. There may be an infinite number of dominoes, and hence no first one. The first mover is not a domino at all, but some agent who sets the whole thing in motion: formally, the agent who arranged the form of the layout in the first place.

Another way of thinking about intermediate movers/actualizers is that they are instrumental. In the sequence:

 A→B→B→...→B→C

None of the intermediate actualizers (B) have the power to make C unless the first actualizer A is concurrently actualizing them. A clarinet does not make music "by itself." Ontologically prior to the clarinet-making-music there must be a clarinetist-making-music "by herself." [We're talking about the music coming-into-existence: i.e., actual sounds being made. The score doesn't actualize the notes.] No one "plays" the musician. If she stops playing, the music stops coming into existence.

Don't worry about the notes lingering in the air after the clarinetist stops playing. "Hearing notes" is not the same thing as "making music." As Jean Buridan noted back in the 14th cent., once momentum is imparted, it keeps going until it is dissipated by a contrary impetus, such as friction or resistance.

4. This concludes to something that cannot be natural. Behind "actual by another" is either something that is not actual or is actual "by itself." But we cannot conclude to something that is not actual, since such a thing would be unable to act, period. So we have to conclude to something "actual by itself." But this purely actual being cannot be a natural being. Natural things are in continual motion/change.

As an analogy consider the thirsty kitten moving across the room. The ultimate source of its motion is a saucer of milk on the other side of the room. This is the first cause of its motion. It is also the final cause of its motion, since it is that "toward which" the motion is directed. But in putting the kitten into motion, the saucer is itself unmoved. It is an unmoved mover -- At least with respect to the  kitten's motion that it actualizes. 

Since the mobile is natural and vice versa, "to conclude to something that acts without being in motion is ipso facto to call it a supernatural cause. [This] is claiming more than that the first mover in the series is immobile with respect to the peculiar motion it causes, since this is true even of, say, the way a bicycle axle is immobile with respect to the wheel or the way an inertial reference frame is immobile with respect to the things moving in it. He’s saying that the mover conveys an actuality without having to change along with the potency it acts on, so, for example, it is like an axle that could be a cause of the wheel moving without having to be in motion along with the wheel, or an inertial reference frame whose boundaries would not change even relative to the mobile thing in it, or like a magnetic field that wouldn’t change and be in flux along with the ferrous objects it tugged on. As an example of natural activity, this is completely crazy, and imagination fails in trying to visualize the sort of mover the First Way is arguing for. The motions one sees around himself all presuppose some kind of supernatural activity." [James Chastek]

5. "And this all realize [is a] divinity." The Latin here reads "et hoc omnes intelligunt deum." The distinction between any old divine being (such as an angel) and capital-G God was not made in medieval Latin, since the use of capitals for that purpose was not yet in vogue. Thomas will spend hundreds of pages and many more Questions to establish that this divinity is what is meant by "God." It's early innings yet, as far as the Summa is concerned.



¹ In the original, Thomas wrote:

Prima autem et manifestior via est, quae sumitur ex parte motus. Certum est enim, et sensu constat, aliqua moveri in hoc mundo. Omne autem quod movetur, ab alio movetur. Nihil enim movetur, nisi secundum quod est in potentia ad illud ad quod movetur, movet autem aliquid secundum quod est actu. Movere enim nihil aliud est quam educere aliquid de potentia in actum, de potentia autem non potest aliquid reduci in actum, nisi per aliquod ens in actu, sicut calidum in actu, ut ignis, facit lignum, quod est calidum in potentia, esse actu calidum, et per hoc movet et alterat ipsum. Non autem est possibile ut idem sit simul in actu et potentia secundum idem, sed solum secundum diversa, quod enim est calidum in actu, non potest simul esse calidum in potentia, sed est simul frigidum in potentia. Impossibile est ergo quod, secundum idem et eodem modo, aliquid sit movens et motum, vel quod moveat seipsum. Omne ergo quod movetur, oportet ab alio moveri. Si ergo id a quo movetur, moveatur, oportet et ipsum ab alio moveri et illud ab alio. Hic autem non est procedere in infinitum, quia sic non esset aliquod primum movens; et per consequens nec aliquod aliud movens, quia moventia secunda non movent nisi per hoc quod sunt mota a primo movente, sicut baculus non movet nisi per hoc quod est motus a manu. Ergo necesse est devenire ad aliquod primum movens, quod a nullo movetur, et hoc omnes intelligunt deum.

The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.