First Way, Part I: A Moving Tale

OK, TOF has finished "In Panic Town, On the Backward Moon" and is ready to resume what he joshingly refers to as "real life."

Back to the Argument from Motion (See Preface)

Getting 'Motional

[T]he arguments require the appreciation of certain metaphysical principles that are unfamiliar or seem archaic to the contemporary philosophical mind...  In particular, the notion of causation employed by Aquinas in the arguments has a decidedly obscure ring to modern ears.
-Oderberg, ‘Whatever is Changing is Being Changed by Something Else’

Part of TOF's herculean effort here will be to translate, as much as he is able, those original items into more modern lingo. This is not always quite possible and not always well-advised, because words in different languages in different eras do not always divide thought into the same categories. But, Excelsior!¹

Clarifications
1. Excelsior. As all men know, this is a packing material used as dunnage.

Since the Argument from Motion involves something called "motion," we may as well address that. Modern science takes motion as axiomatic, and therefore never comes to grips with it. Science deals with how motion is effected¹ or altered, but never with what motion is. More often than not, it is restricted to one kind of motion: to changes of location -- electrons through a wire, planets through space, blood through the vessels, photons through slits², etc. But what motion is per se is a matter for metaphysicians.

Parmenides had held that motion is an illusion suffered by consciousness³, and his pupil Zeno illustrated this with a series of paradoxes. Moderns usually dismiss the paradoxes in the belief that convergent infinite series have resolved the issue. But convergent series provide only a mathematical model, and do not address the physical problem of motion. For this, we need the long-forgotten Aristotelian rebuttal: that of potency and act. [cf. Augros, scroll to Continuity of Motion]

Clarifications
1. effected. Yes, not affected.
2. or not.
3. illusion. Parmenides was much like a Late Modern in this respect, since the Late Modern also ascribes to illusion such things as color, pain, free will, the self... The last one entangles the bien pensants in a rather sticky logical briar patch. Whose illusion was that?

A Potent Act

1. Rock = Parmenides, who taught that "no thing comes from nothing." Hence, etc., etc., there can be no change. Parmenides tried to change people's minds about this.

2. Hard Place = Heraclitus, who taught that motion was everything and reality was a chaotic flux.

"Don't Move!"
Inventor of Chicken Parm

The realists, like Plato and Aristotle, tried to explain how Parmenides was wrong without tumbling into the opposite absurdity of Heraclitus. How can a body change without being able to change into anything? How can an apple change from green to red, but not from green to purple polka-dots or from green to triangular. Plato tried one solution, but wound up with a third realm of existence, the Ideals. Aristotle was dissatisfied with this and took a more empirical approach. The reason Late Moderns often "don't get" potency and act is because they are answers to questions they have forgotten were ever asked. They simply assume Parmenides was stoopid.

Since Aristotle wrote in Greek, we must understand his words, and that is not always easy. He uses two words --energeia and entelechia-- interchangeably. But energeia means being-at-work and entelechia means being-at-an-end. Compare the English words "building" and "building." One is a participle of a verb and means building-at-work; the other is a noun and means a building-at-the-end. If I am building a building, the distinction becomes clear. What Aristotle means by act (or "actuality") is... both. Simultaneously. To be a thing in the world is to be at work.¹ For Aristotle, actuality is therefore close in meaning to what it is to be alive.² [Sachs, IEP]

A building a-building

Thomas Aquinas showed how "building a building" was 

1. not a contradiction and 
2. a genuine definition of motion.  

English is fortunate to possess the present progressive tense, which helps us express this better. When we say that the puppy is growing or that the apple is ripening we mean that the puppy or apple is not merely "the complex of characteristics it possesses right now," but also that something that it is growing toward or ripening toward: that-toward-which it is, right this moment, ordered. The "that-toward-which" is called the final cause or telos. To say that something is in motion [kinesis] is just to say that it is both what-it-is and that-toward-which. To speak scientificalistically, it is its current location and its vector. [Sachs, IEP]

Actualization? Kinesis? Hunh?

What's in a name?  If "motion" is more than the thin concept used in modern physics, that raises the question³ of whether we ought to call it "motion" anymore. Because motion is defined as "the reduction potency to act," we might call it "actualization," but this would earn blank stares [see left]. So would kinesis, although that sounds agreeably scientificalistic. The word change captures the greater scope of kinesis, but comes off as rather bland. It's kinetic change, after all. It's "on the move!" TOF will be eclectic in this essay, using all four terms more-or-less interchangeably. Don't come crying to TOF afterward with some semantic quibble. You Have Been Warned.

 

Clarifications:
1. Aristotle said "to be is to do." Sartre said "to do is to be." Sinatra otoh said, "do be do be do."
2. What it is to be alive. Compare similar comments in the series In Psearch of Psyche. Modern philosophers typically regard efficient causality (i.e., "agency") as due to rational agents only. Hence, either the rest of nature lacks agency or (rejecting agency altogether) humans lack agency also. Aristotelians, otoh, regard human agency as simply "a higher-order manifestation of a feature shared by every primary substance in the universe." These lower-order things serve as stepping stones to grasping higher-order things.
3. raises the question. It does NOT, as in NOT, "beg" the question. TOF is going insane, having seen and heard this misuse numerous times just over the past week alone on TV and Internet. It's enough to drive an Irishman to drink. OK, that's not a drive, it's a putt, but you catch the drift.

Just When You Thought It Was Safe To Get Back in the Discussion

Da Man
All power to the Movement!

Now that we realize that some things we hadn't thought of as motions are actually motions -- ripening apples, growing puppies -- we encounter the unsettling thought that some things we had though of as motions are actually not.

Motion is an alteration to something the body already has. If an apple has greenness (greenitude?) and it is altered to redness, that is a "motion." It actualizes a potential-to-be-red. It is an alteration to the green that the apple already has.

But Aristotle regarded the orbiting heavenly spheres as being in a state of rest. WTF? says the confused Late Modern. [See glyph, above, left.] How can an orbiting planet be at freaking rest?

Because the "ever-running" circular¹ movement is not changing. 

The same thing applies to a body in unchanging rectilinear motion; so-called inertial motion. The body already has the motion. So kinesis would mean a change to this motion. Hence, Aristotelian "kinesis" is more like "acceleration" than "velocity."²

So to the question of "what accounts for the change of location of an inertial body," the answer is, "whatever imparted the motion originally." This might be a rocket engine that lifted an interstellar probe and set it free. It might be a Mars-body that struck the Earth and took a divot the size of the Moon. It might be a supernova throwing starstuff far and wide into the Void. But in any case, the impetus³, as Jean Buridan said back in the 14th century, does not change until countered by a contrary or dissipative impetus. In that case, the change in the motion is due to the contrary force, just as Newton would later reiterate.

"When you shove a millstone, the motion or change is that of imparting momentum to the millstone. When the millstone moves, or continues to move after that, the motion is change of position owing to momentum [already] possessed by the millstone. Something that has momentum will continue to change its position until acted upon by some force (that's what momentum is). Something that does not have momentum will not suddenly get it out of nowhere. That's as true for modern physics as for the Aristotelian variety. Indeed, the continued motion of the millstone in empty space is the very same principle at work: the millstone will not undergo change (such as losing momentum it already has) without some cause (e.g. friction) continuing to act on it. Remov[e] the pushing cause, and the effect of getting more momentum does indeed cease; remove the retarding cause (friction), and the effect of losing momentum will likewise cease."
[Feser, 2014, emph. added]

A Modern term that captures this idea of "rest" as "not changing" is equilibrium state.

Not the act of building materials

The motion of a thing is always toward something which that thing has in potential, and a motion consists in some sense of being what-it-is-now and what-it-is-going-to-be. The original potency is made actual in two ways.

A set of building materials has the potential to become a house. It also has the potential to become a barn for storing grain, a scaffold for dealing with impertinent comm boxers, a grandstand for others to watch the aforesaid entertainment, or it may remain a set of building materials. It does not have the potential to become an aardvark, so it's not Heraclitus' "Anything Goes."

Bacon's big blue bouncy ball in motion toward red

When construction begins, the "wave function" of all those various potentialities collapses to a particular potential aimed at the one particular end. This is the first act: the potency becomes an "actual potency." The second act is when the kinesis reaches its equilibrium state (final cause): the house is actually finished. Between the first and second act there is an intermission.

Ho ho, TOF jests. Between the first and second acts is what Aristotle called 'motion' or kinesis. 

BTW, "building" in either sense is not the actualization of the house. It is the actualization of the building materials.

Clarifications:
1. circular. TOF of course speaks elliptically.
2. acceleration/velocity. Note that these are medieval terms. They did not exist in ancient Greek. Sapir-Whorf notwithstanding, this did not prevent Aristotle from thinking about velocity and acceleration; but it did prevent him from thinking and writing concisely. The same may be said of the lack of a present progressive tense in Greek and Latin. In English we can say "it is changing" but in Latin and Greek we must content ourselves with "it changes" which doesn't quite have the same sense of happening-right-now.
3. impetus. Buridan held that impetus was proportional to the weight and speed of the body. The Modern will immediately recognize this as "momentum," which is the product of mass and velocity. Plus ça change, plus c'est la même chose.

The ablative of motion?
Alas, no abs.

Summa Motus

Lets sum it up, motus-wise.

1. "Motion" is a kinetic change from a state of potency to a state of actuality in any of the categories, esp.: location, quality, and quantity.  Such motions include growing puppies, ripening fruit, generation, morphogenesis, decay, and so on.
2. A potency cannot be just anything at all, but something which the thing can become through its own nature, as when a puppy matures into a dog or a green apple ripens to red. [We may also allow what a thing can become by artifice: we can paint the apple with purple polka-dots. But art has never puzzled anyone.]
3. "Motion" begins when the many potencies a thing possesses collapse onto a single potency (the "actual" potency). The act of building commences.
4. "Motion" ceases when the potency has been fully actualized (or the actualizing force has been removed!) The building has been completed (or abandoned). 
5. "Motion" means that a thing is both what it is now and what it is going to be, as of now.
6. "Motion" is a change to something a thing already possesses. If the thing already possesses motion, then it would be a change in that motion (i.e., an acceleration)
7. "Impetus," or momentum, remains with the thing unless dissipated by a contrary impetus. Hence, a body in space keeps going because of its original impetus.
8. "Inertia" (lit. "laziness") is a principle of resistance to change, not a principle of motion. "Motion" ["Change"] must overcome this resistance. A body does not continue to move because of inertia, but because of momentum. If friction changes the motion, it must overcome resistance to change.
9. "Motion" that is continuous and unchanging is actually "rest" (equilibrium). This includes orbiting planets, Belousov–Zhabotinsky reactions, etc. 

Next Exciting Episode: Two Lemmas Make Lemma-aid (link now active!)

 

Indicium Librorum

1. Aristotle. The Physics, Book VI. Book VIII
2. Augros, Michael. "A ‘Bigger’ Physics," The Institute for the Study of Nature, Jan. 28, 2009 (MIT)
3. Feser, Edward. "Clarke on the stock caricature of First Cause arguments," (Feser blog, Jul 12, 2014)
4. Feser, Edward. "The medieval principle of motion and the modern principle of inertia" in Proceedings of the Society for Medieval Logic and Metaphysics, Vol.10, 2012.
5. Sachs, Joe. "Aristotle: Motion and its Place in Nature" (Internet Encyclopedia of Philosophy)
6. Thomas Aquinas. Summa contra gentiles, I.13, (Dominican House of Studies)
7. Thomas Aquinas. Summa theologica, I Q2 art.3, (Dominican House of Studies)
8. Thomas Aquinas. Compendium theologiae, Bk.1 ch.3, (Dominican House of Studies)
9. TOF. In Psearch of Psyche: Some Groundwork. (The TOF Spot, July 11, 2014)
10. TOF. America's Next Top Model, (The TOF Spot, February 4, 2014)