Stage II

Considered as an argument for the existence of God, G2 is spoiled by the failure of its first stage. But in its subsequent analysis of the notion of a first mover, it makes a contribution that is perhaps unique among Aquinas's existence arguments. He calls attention to the fact that stage II involves a fresh start. Here's how he makes the transition from stage I to stage II in the parallel argument in his Physics commentary: 'But that first [mover]'—the one inferred in stage I of G2—'must be either immovable or a self-mover', since stage I's conclusion is only that there is a first mover that is not moved by anything extrinsic to it. 'Therefore, we have to consider end p.72


© Copyright Oxford University Press, 2006. All Rights Reserved that which moves itself, on this basis making another beginning of our consideration'(In Phys. VIII: L9.1049).

But because when we have the conclusion that there is a first mover that is not moved by something else that is extrinsic to it, it does not follow that it is immovable inwardly (penitus), Aristotle goes further, by saying that this can occur in two ways. In one way, so that the first [mover] is immovable inwardly. If we suppose that, then we have the thesis—namely, that there is an immovable first mover. In the other way, so that the first [mover] is moved by itself. (And that seems probable, because what occurs on its own is always prior to what occurs in virtue of something else. That is why as regards moved things, too, it is reasonable that the first thing moved be moved by itself, not by anything else.)

But, given this, the same thing follows again.

42 i.e. 'even if one should arrive at a first [mover] that is a self-mover, one must none the less come to a first [mover] that is immovable' (In Phys. VIII: L10.1050).

For it cannot be said that [in the case of] a self-mover the whole is moved by the whole, because then absurdities discussed earlier would follow—I mean [such absurdities as] that someone would at the same time be teaching and be taught (and similarly as regards other motions), and, again, that something would be in potentiality and actuality at the same time [and in the same respect], (For what is acting as a mover, considered just as such, is in a state of actuality, but what is being moved [considered just as such] is in a state of potentiality.) We are left, therefore, with the conclusion that one part of it is a mover only, and the other part [is what is] moved. And so we have the same as before—namely, that something is an immovable mover.

But one cannot say that both parts are moved, the one by the other [and vice versa], or that the one part moves itself and moves the other, or that the whole moves a part, or that a part moves the whole, because absurdities brought out earlier would follow—I mean [such absurdities as] that something would at the same time move something and be moved in accordance with the same species of motion, and that it would at the same time be in potentiality and actuality, and, further, that the whole would not be moving itself first but rather by reason of a part. We are left, therefore, with the conclusion that in the case of a self-mover one part must be

immovable and the mover of the other part. (13.101-2)

43 Cf. Physics VIII 5, 257bl3-258a5; In Phys. VIII: L9.1049; L10.1052-61.

Any mover that at least sometimes moves something when it is not being moved by anything extrinsic to it is on such occasions, and in virtue of that fact alone, a first mover. And nature certainly seems end p.73


© Copyright Oxford University Press, 2006. All Rights Reserved to include innumerable series of movers and moved things in short causal chains whose first links are movers that are moved intrinsically if at all. MacDonald calls such familiar, apparent first movers 'mundane' (1991a: 147). You, for instance, are a mundane first mover whenever you do something just because you feel like doing it. The notion won't be left at that uncritical level for long, since Aquinas is heading toward the consideration of just such familiar, mundane, first movers in the a posteriori stage of G2.

Animals, the mundane first movers we're familiar with, seem to be self-movers on many ordinary occasions. But anyone who, like Aquinas, subscribes to the OQM principle must take the very notion of a self-mover to be incoherent theoretically. If'Everything that is moved is moved by something else', then, strictly speaking,1nothing moves itself', as Aquinas expressly concludes in the course of supporting OQM as the first premiss of argument G1 (13.89). However, the conclusion of G2's stage II speaks less strictly, appearing to countenance the notion of a self-mover as long as it is

analysed in just one particular way of the six ways considered in stage II.

44 This provisional approach to the notion of a self-mover is plainly and succinctly expressed in the clause of his Physics commentary immediately prior to his taking up this analysis: 'on this basis making another beginning of our consideration—I mean, so that //anything moves itself, we might consider how that is possible' (VIII: L9.1049).

According to the first, and only strict, analysis of self-mover, (1) if X can be considered a self-mover, then, of course, X is the mover, and X is what X moves; and so 'the whole [of X] is moved by the whole' of X (line 13). But,

alluding to two 'absurdities discussed earlier',

45 The first is in G2's stage lb, the second in the strongest of the sub-arguments supporting principle OQM in G1 (13.89).

Aquinas here dismisses this first analysis (which yields what might be called strict self-moving) as entailing an impossibility. And I think he's clearly right to do so on either basis, though it may be more instructive in this context to see how he means to do it on the basis of the discounted stage lb. For although, as I've claimed, X's moving something else, Y (which is what's at issue in stage lb) with a most specific species of motion M i is not incompatible with X's being moved with M i , at least indirectly, there are no ways out of incompatibility when it's the whole of X itself that's doing the moving and the whole of X itself that's then being moved. You cannot be at once both altogether the one teaching and altogether end p.74


© Copyright Oxford University Press, 2006. All Rights Reserved the one learning theorem 45, both the one who already understands it and

the one who doesn't understand it yet.

46 'In this way, therefore, it will follow, further, that a person will be teaching and being taught at the same time with respect to one and the same knowable object'—which is absurd (In Phys. VIII: L10.1052).

And so any analysis of self-mover that might be taken seriously will have to begin by allowing an unstrict interpretation of the concept.

Aquinas says (lines 20-2) that already at this point we're left with the conclusion that one part of X is a mover only, while the other (complementary) part of X is what is moved by that moving part of X. But he's really anticipating the final conclusion of stage II, which he restates (lines 32-4) after dismissing four other possible analyses of self-mover, broadly conceived of. These analyses of X as a 'self-mover' are (2) that the whole of X moves a part of it, (3) that a part moves the whole, (4) that one of two complementary parts moves itself and the other part, and (5) that two complementary parts move each other. Besides the two absurdities he used in dismissing analysis 1, Aquinas alludes here (lines 31-2) to a third

previously derived absurd conclusion.

47 This absurdity, too, is found in argument G1 in support of principle OQM (13.85). It may be intended as the basis on which to rule out analysis 5, which might also be dismissed simply on the grounds that it offers a circular explanation

of motion.

48 The only reason for taking the notion of a self-mover seriously at this stage of the argument is that such a thing may seem to provide a viable alternative to an altogether unmoved mover for the role of a cosmic first mover that might count as God. But, as Aquinas explains in the parallel passage, 'If each of the two [complementary] parts of a whole self-mover moves the other part reciprocally, one of them is no more a mover than the other is. But a first mover is more of a mover than a secondary mover is. Therefore, neither of those [parts] will be a first mover. That is absurd, because in that case it would follow that that which is moved from within itself (exseipso) would be no nearer [an approximation] to the first source of motion—the one that is second to none (quod nullum sequitur esse)— than that which is moved by something else' (In Phys. VIII: L10.1055).

Either of the two absurdities already invoked will do the job for analyses 2-4.

The last analysis of 'self-mover' X is the one Aquinas favours here: (6) that one of two complementary parts of X is 'a mover only'—that is, is an

immovable mover—and the other part is what that first part moves.

49 In his Physics commentary Aquinas is a little more forthcoming about the status of the part that does the moving: 'If regarding the part of a self-mover that does the moving we are given [the hypothesis] that it moves itself as a whole, then it follows, on the basis of things already proved, that, again, one part of that part does the moving and the other part of it is moved. For it has already been shown above [VIII: L10.1052] that the only way a whole moves itself is that one part of it does the moving and the other is moved. . . . We are, therefore, left with the conclusion that the part that does the moving in a self-mover is altogether immovable' (VIII: L10.1061). Aquinas's Aristotelian analysis of self-movers is carried forward throughout VIII: Lll. 1062-8 in ways that illuminate the analysis in L10, but without adding anything essential to argument G2.

Not only does analysis 6 steer clear of the end p.75

Kretzmann, Norman , (deceased) formerly Susan Linn Sage Professor Emeritus of Philosophy, Cornell University, New York

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