03 July 2013

Attempting to Follow the First Way

I.  A reader recently requested a response to some pretty bad objections to St. Thomas's first way (aka the "Argument from Motion").  Since I'd been planning on working through the five ways, but was really paralyzed by the difficulty of the task, I took the request as a prompt to get this one done with.  I should preface my remarks by admitting that when I started working through it (and for the past year or so) I had very little confidence that the first way actually proves God's existence.  However, I gave it my best, or at least seven so hours over a few days, and I find it, as outlined here (which is expanded greatly beyond the original Summa text, obviously) moderately compelling, though not absolutely (see [T] below).

II.  First, let's have the text in front of us.  

Respondeo dicendum quod Deum esse quinque viis probari potest. 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 toactuality. 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.

II.  It cannot be stressed enough with commonly excerpted texts like ST Ia q.2 a.3 that Thomas is writing for "beginners in theology," that is, people who have already completed several years of graduate study in (Aristotelian) philosophy.  He doesn't explain a lot of his concepts in great depth, and sometimes leaves important premises undemonstrated, because he assumes that his readers already have a high degree of familiarity with them.  Most people who read ST Ia q.2 have no familiarity with these concepts and principles at all.  So we've got to do bit of preliminary legwork.  

III.  POTENCY / ACT : St. Thomas distinguishes between the potency or "potentiality" of a thing and its act or "actuality".  What does this mean, and how does he come by this distinction?  Suppose I love making things with apples (apple butter, apple sauce, apple pies, apple cakes, caramel apples, you name it).  When I bring home a sack of apples and set them down in my kitchen, I know that they may some day become sauce or pie, even though they aren't yet.  The apples are "in potency" to become pie, but in actuality, they aren't pie.  They're still just apples, and despite this "potency" they may never become pie.  I may, from forgetfulness or mere spite, decide to let them rot instead.  Things capable of changing are in potency to become different from what they are, presently, in act.  This is extremely common-sensical, and one would have to embrace a radically indeterminate view of the world or of change in order to get around it.  (Quantum Physics people sometimes take such a line, but the fact that the physics community has yet to give an account of what's going on in wave function collapse makes it difficult to take them seriously as philosophers.  Let alone the numerous obvious philosophical objections to a metaphysics of radical indeterminacy, which I won't get into here.)

IV.  So we have the distinction between act (what a thing is, actually, right now) and potency (what it can be made into or is capable of becoming, by whatever process).

V.  Now we define MOTION : Motion is simply any change from potency to act.  Motion is a specialized term for Aristotelians and Thomists.  It doesn't just mean "a change in place", it means any kind of change.  To Move, in the Aristotelian sense, is to realize some theretofore unrealized possibility for being or acting—to make what was possible, actual.  With those preliminary explanations out of the way, we can run through the argument.


The argument divides cleanly into two parts: first, a defense of the proposition that Whatever is moved is moved by another.  Second, a demonstration of the impossibility of an infinite chain of movers.  If we accept these two points, plus the minor premise (A), it follows that there must be an unmoved mover.  Let's look at the full argument in detail.

A. It is clear from experience that some things are in motion. (Pretty obvious.)

B. One thing can move another only insofar as the it (the mover) is in act. (I.e., non-existing things cannot be the cause of motion.)

C. Nothing can be moved unless it is in potency to whatever it's being moved toward.  (Since motion is defined above as a reduction from potency to act, this is pretty much tautological.)

D. A thing cannot be in potency and in act in the same respect at the same time.  (Since to be in potency to something is not yet to be that thing and to be in act is already to be that thing, this follows by the principle of non-contradiction.)

E. Therefore, nothing can, in the same respect at the same time be both mover and moved, i.e., nothing can move itself. (This follows cleanly from [D] and the definition of motion.)

F. Therefore, whatever is moved is moved by another. (This follows from E.  Note that thus far, the only really questionable premise is [B], which itself seems fairly commonsensical.)

G. Now, in any particular case, that which moves another thing is, in the act of moving another, either itself unmoved, or is moved.  (This is tautologous.)

H. However, since motion is the reduction from potency to act, if the mover itself changes in the process of moving another, we must say that it is also moved by another.

I.  Next, Aquinas says (without much further explanation) that in the absence of an unmoved mover we would have to postulate an infinite regress in the order of movers (A is actualized by B being actualized by C being actualized by D....).

J.  Now, if the infinite regress were temporally extended (like a series of dominos), so that A was actualized by B, which had earlier been actualized by C, etc., we would not have a problem.  Aquinas himself affirms the possibility of that sort of infinite regress later on in theSumma .  One need not postulate an absolute beginning for any sequential series of causes.  There's nothing irrational (setting aside empirical evidence to the contrary) about saying that things have been bouncing around in space for an eternity.

K.  So, what kind of infinite regress is Aquinas talking about here?  Let's look at a concrete example.  Suppose we have two big blocks of concrete floating through space.  A fast moving block hits a slow moving block.  As a result, the slow block speeds up and the fast block slows down.  In the first instance we would simply say that the first block moved the second.  But of course, the first block was likewise moved in the interaction (it slowed down).  So, as masters of newton's third law, we say that each object moved the other.  The slow one, by its inertia, conveyed an impulse to the fast one, and vice versa.  But let's focus in on the impulse itself.  We can think of the two blocks, at the point of their collision, as a single object, undergoing a change.  But obviously there's nothing intrinsic about two blocks placed next to each other that would lead to their springing apart a moment later (as these will).  In other words, if there's a reduction from potency to act in our object, we need to ask what is actualizing it.  What moves the blocks apart?

L.  Well, physics tells us that the transfer of impulses in the moment of the collision (which is not instantaneous, but let's focus on a single instant of it to keep things clean), is caused by the interactions of the electrons on the surfaces of the two blocks.  The Pauli exclusion principle, properly aligned orbitals, etc., lead to the distribution of a large-scale shift in electron clouds throughout both of the objects, and the qualities of this shift determine the elasticity of the collision.  Cool.  But let's stop at these electromagnetic interactions.  Let's focus in on a particular interaction between two electrons.  Based on my extremely limited amateur knowledge (forgive me!) the interaction can be described in either of two ways: as a feynman interaction involving the exchange of a force-carrying photon, or as the transmission of a change in the surrounding electromagnetic field, which transmits an impulse to the electron.  Either way, we've ended up with a quantized version of our original setup.  I.e., what's moving our composite two-block object is just another composite three-object system (electron, electron, field/boson).  And here we can repeat the process again.  An impulse is communicated from electron A to electron B, meaning that in some moment the two are both actualized.  So we take them as a single thing.  What causes this little electron interaction system?  What actualizes it?  Why does it behave this way?

M.  A brief aside.  Hopefully, we're starting to get a sense of the kind of regression Aquinas is interested in.  As already established, it isn't a regression of sequential changes; but it also (in case the reduction to electrons made it seem that way) isn't a regression to fundamental parts.  It's a reduction to motive principles, i.e. to the motive principle which leads a thing to change.

N.  Back to our electrons.  At this point when we ask "what moves the electrons/field/boson?" the inclination of the normal person would be to say either "the field" or "the laws of electromagnetism" (to which the field is going to have to be reduced at some point anyway).  But what *are* the laws of electromagnetism, anyway?  How do they (ostensibly) cause these concrete wave/particle things to change?  Are the laws of electromagnetism an independently existing reality, or a consistent feature of electromagnetic particles?  Let's assume we go with the latter (the former would lead us into weird subsistent-numerical-principles territory).  In this case, we have to say that particles actualize themselves, i.e. that they are the cause of their own particular way of acting, and that they elicit from themselves the properties observed in laboratories which are gathered in abstract under the name "laws of electromagnetism."  In other words, it seems that we have to say that there are some things that move (both transitively and intransitively) without being moved.

O.  But hold on, I thought we showed earlier that logically speaking, everything moved is moved by another, i.e., things just can't be the reason for their own actualization?  There must be a way of getting around this without admitting the existence of an unmoved mover.  Well, one option is to postulate another layer of interactions below the electrons we were talking about before.  But it seems clear that if we do that, we're just deferring the inevitable.  A second option is to create a closed explanatory loop.  But again, this kind of solution has been tried (at the very beginning, in our appeal to newton's third law), and when it is applied, the question of the principle of motion remains unanswered for the system as a whole.  Another option, and probably the most powerful remaining (also the most popular), is to deliberately draw a blank — to say that there is no motive principle.  Fields do not move themselves, and nothing else moves them.  They simply are that way.  

P.  There's a soothing nihilism to this last option, but it leaves a bizarre problem unsolved: what moves things to act when they do?  If they have natures, what actualizes those natures?  What motivates things to follow the "forces" and "laws" that we see consistently worked out on the smallest scales?  The question is not about the horizontal succession of movers, but the "vertical" succession: what orders things to these sorts of behaviors, these potentialities, these tendencies?  What gives the rule to nature, or bends nature to follow the rules we observe?  If these questions are to have any answer, it seems that we have to give in and accept the existence of an unmoved mover.


Q.  "Not so fast, Tommy boy! Suppose we go the pythagorean route, and postulate the existence of transcendental subsisting laws which order the world.  There's an unmoved mover for you.  How about that?  Let mathematical physics be our god."  At this point, Aquinas would be perfectly happy to accept some sort of quasi-pythagorean law-deity.  The task of winnowing down the precise attributes of this thing the existence of which we have just demonstrate is left to the next two dozen questions.  What sort of deity he proves it to be is a question that transcends the scope of this argument.

R.  "But you're saying there's some being that moves other things without itself changing.  Isn't that a contradiction?  Surely if something changes something else, it must itself change."  How does that follow exactly?  Oh wait, it doesn't.

S.  "But inertial motion requires no mover to explain it."  Actually, if we take an inertial object as our central illustration, the argument works out pretty much the same way.  An inertially moving object is either (1) perfectly inertial, in which case it isn't interacting with *anything* and there's no way of even saying that it's moving, because it's so totally isolated from the rest of the universe, in which case its "inertial motion" isn't really motion in any meaningful way, OR (2) imperfectly inertial, in which case its movement is detectable within some system, which means that we can take that system as a composite object in motion (in the technical sense outlined above), and pursue the line same line of thought as before.

T.  "But really, this is just an intellectual game.  You're insisting on creating a certain type of conceptual empty space, so that you can then demand that we fill it with God.  I refuse to acknowledge the necessity of this way of setting up the terms and concepts of the discussion."  Good objection!  But I'd like to hear a coherent alternative.  Then we could have a really interesting conversation.  As things stand, the only alternatives involve the denial of the reality of motion.  I.e., either things don't change and the appearance of change is an illusion cast by the mind in interpreting the world (i.e. parmenides/kant) or things don't change because when something ceases to be precisely what it was at a given moment, it ceases to exist altogether, and something new exists instead (Heraclitus and friends).  These are both, I confess, pretty awesome theories, and they're fun to think about, but they certainly can't be called reasonable theories, because what they defy is precisely the central rational habit of isolating and identifying principles.  But maybe there are alternative ways of undoing our argument that can't be reduced to these!  A world of possibilities awaits.

U.  Finally, one of the most common objections: "But the world doesn't need to have had a beginning.  How can you pretend to have demonstrated the existence of a prime mover if it's rationally indeterminable whether the world ever began to exist?"  Well, friend, actually if you read any of the above (granted, it's a little long), you would have learned that the "prime mover" argument has nothing to do with temporal succession at all.  Even if the world never had a beginning and had always existed, it would still hold just as well as it does.