Since I make all of this clear in the book, I don’t know why he so badly misreads the argument, unless it is because (to paraphrase Wittgenstein) a picture is holding him captive. That picture is scientism, the thesis that the questions and methods of empirical science are the only real questions and methods there are. Since scientism itself is not an empirical hypothesis, not something the truth or falsity of which can be established by empirical scientific means, it is (when not so qualified as to be no longer interesting) self-undermining. Somehow that never seems to weaken its grip over those beguiled by it, despite their oft-purported superior rationality. Having once hit upon the idea – usually as a reaction against some body of religious doctrine they’ve become disillusioned with – they fall absolutely head over heels in love with it and become insensitive to criticism. Scientism just can’t be wrong, you see, because when they first became aware that there was something called “reason” as opposed to “faith,” that reason appeared to them in scientistic form, and to abandon the scientism would seem to them to be to abandon reason too. This is tosh, but tosh that is all the more powerful to the extent that those who buy into it think themselves for that reason uniquely immune to tosh. It is no wonder, then, that despite the fact that I explain all of this too in the book, UnBeguiled remains UnUnBeguiled.
Anyway, be all that as it may: What UnBeguiled’s (apparent) scientism keeps him from seeing is that Aristotelian-Thomistic arguments for God’s existence do not take as their starting points premises to which empirical science as that field of study is understood today is relevant. They begin instead from premises that any such science must take for granted. (That is not to say that “physics” in some sense of the word is not relevant to an argument from motion, since the boundaries between science and philosophy are not carved up in Aristotelian-Thomistic philosophy the way they are by other traditions in philosophy. The point is just that the sort of premises that an argument from motion starts from would, the way things tend to be carved up by most scientists and philosophers today, better be thought of as claims in metaphysics or philosophy of nature rather than physics per se.)
In the case at hand, what is relevant is the actuality/potentiality (or act/potency) distinction. As those familiar with the history of ancient philosophy (and TLS readers) know, the origin of this distinction lies in Aristotle’s response to Parmenides. Parmenides attempted to demonstrate a priori that change is impossible. Aristotle responded, in part, that we can understand how change is possible when we see that there is, in addition to being and non-being (the notions Parmenides makes use of), the third category of what exists potentially – that which is not actual and may never be actualized, but which is not nothing either. Hence it is not enough to say of a rubber ball (to make use of an example from TLS) that it is actually solid and spherical but not actually melted and not actually the number 23. For it is melted in potency or potentially, but it is not the number 23 even potentially. Once we see this, we can see why change is possible: the ball can melt because in doing so it is not going from sheer non-being to being (which Parmenides argued was incoherent) but rather from being in potency to being in actuality.
There are other reasons why we must recognize an act/potency distinction. For example (and for reasons I spell out in TLS and have alluded to in previous posts), we have to recognize in all efficient causes something like final causality or directedness toward an end if we are to make causation intelligible at all. But to recognize this is to recognize the existence of potency as distinct from act, since a cause that is directed toward the generation of some effect even when it hasn’t yet actually generated it is in potency relative to such generation. The point, though, is that this whole discussion takes place at a deeper level than empirical science. Empirical science studies particular changes and causes; metaphysics or philosophy of nature studies the preconditions of there being any changes or causes at all. Empirical science reveals to us the specific mechanisms by which the reduction of potency to act (to put it the way the Scholastics would) occurs in this or that specific domain within the natural world; metaphysics or philosophy of nature reveals to us that such a reduction must underlie whatever those mechanisms turn out to be.
For Aristotle and the tradition he inaugurated, the most important instances of reduction of potency to act involved essentially ordered series in which some causes were instrumental relative to others (and of which simultaneous causes and effects are the most obvious examples). UnBeguiled insinuates that the notion of a per se or essentially ordered causal series is something trumped up for the purposes of religious apologetics. In fact it is nothing of the kind, unless you think Aristotle and other pagans were frantically concerned to prepare the way, millennia in advance, for Josh McDowell.
The sort of example that in TLS I follow Aquinas in using, viz. a hand’s using a stick to move a stone, is (as I note in the book) just an illustration to generate the key concepts; strictly speaking, a hand isn’t a first mover. And strictly speaking, quibbles over whether the movement of the stick occurs at exactly one and the same instant of time as the movement of the stone are not to the point either. As I emphasize in the book – and this is something UnBeguiled omits to mention – ultimately the stone, stick, and hand all depend for their very existence at any moment (forget about their movements through space) on the actualization of various potentials. For the muscles to exist here and now the potentiality of their constituent cells to constitute muscles must be actualized here and now; for the cells to be actualized in that potential, the potential of the molecules making up the cells to constitute cells must itself be actualized here and now; and so forth. This does imply simultaneity, but notice that (a) the point has nothing to do with acceleration, change of spatial location, etc., and (b) the point isn’t so much that the members of the series are simultaneous (though they are) but that they are essentially ordered: no molecules, no cells, no muscles.
The length of the series is irrelevant. As other Thomists have noted, even if an essentially ordered causal series could per impossibile go back infinitely far, since none of the causes in it have any intrinsic causal power there would have to be some purely actual unmoved mover outside it which keeps it operative. And by the same token, if there were even a single actualization of a potency, that too would suffice to lead us to a purely actual unmoved mover. Look around you; or don’t look around, just contemplate your own thoughts. Is there any actualization of a potential at all? Why, yes there is – and Boom, you’ve got your unmoved mover, whether immediately or at the end of a series. (Supposing the argument from motion is free of other problems, that is – here I’m just addressing the claims UnBeguiled makes.)
And lest UnBeguiled seek to quibble now over physiology, I should emphasize that the specific empirical details here are irrelevant as well. Whatever the details of the physics, chemistry, or physiology turn out to be, they are all going to involve the reduction of potency to act in essentially ordered causal series, because any material world at all is going to involve that. And that is all that matters for the argument. This is not “imaginary physics,” but the metaphysical precondition of there being any non-imaginary physical world at all. To refute the argument, then, it will not do simply to shout “Science!” What is needed is a serious philosophical evaluation; more Thomas Aquinas, less Thomas Dolby.