Edwards does realize that Aquinas is not arguing that the universe must have had a beginning – that the first cause he is arguing for is “first” not in a temporal sense, but in an ontological sense, a sustaining cause of the world here and now and at any moment at which the world exists at all. Still, he thinks this fails to address the heart of the atheist’s critique. For why might a series of causes existing simultaneously, all here and now, not be as infinite as a temporal regress of causes might be (by Aquinas’s own admission)? And if there must be a first uncaused cause in the order of simultaneous causes, why could it not be something other than God, such as basic material particles or gravitational forces?
The very asking of these questions shows that Edwards does not understand the distinction between causal series ordered per accidens and causal series ordered per se, on which the Thomistic arguments (like other Scholastic cosmological arguments) crucially depend. Following Joyce, Edwards refers instead to the distinction between causes in fieri and causes in esse, which might be part of the problem. Not that there is anything wrong with Joyce’s terminology, but it might suggest to someone otherwise unfamiliar with the Thomistic and Scholastic arguments – as it apparently did to Edwards – that the difference between “becoming” and “being” is what is supposed to be the key to seeing why the second sort of causal series cannot in the Thomist’s view be infinite. And that is not the case.
What is key is the distinction between instrumental and principal causality (or second and first causality), a distinction which the language of per accidens versus per se (which I use in The Last Superstition and Aquinas) better conveys. An instrumental cause is one that derives whatever causal power it has from something else. To use Aquinas’s famous example, the stick that the hand uses to push the stone has no power to push the stone on its own, but derives its stone-moving power from the hand, which uses it as an “instrument.” (Of course, the stick might have some other causal powers apart from the hand; the point is that relative to the specific series hand-stick-stone it has no independent causal power.) A principal cause is one that does have its causal power inherently. The hand in our example can be thought of for purposes of illustration as such a cause, though of course ultimately it is not, since its power to move the stick depends on other factors. Indeed, there can at the end of the day be only one cause which is principal or non-instrumental in an unqualified sense, namely a cause which is purely actual and thus need not be actualized in any way whatsoever by anything else. In any event, it is because all the causes in such a series other than the first are instrumental in this way that they are said to be ordered per se or “essentially,” for their being causes at all depends essentially on the activity of that which uses them as instruments. By contrast, causes ordered per accidens or “accidentally” do not essentially depend for their efficacy on the activity of earlier causes in the series. To use Aquinas’s example, a father possesses the power to generate sons independently of the activity of his own father, so that a series of fathers and sons is in that sense ordered per accidens rather than per se (though each member of such a series is also dependent in various other respects on causal series ordered per se).
So, it is ultimately their instrumental character, and not their simultaneity, which makes every member of a per se ordered causal series other than the first depend necessarily on the first. To be sure, the paradigm cases of causal series ordered per se involve simultaneity, because the simultaneity of the causes in these examples helps us to see their instrumental character. And the Thomist does hold that the world must ultimately be sustained at every instant by a purely actual uncaused cause, not merely generated at some point in the past. For these reasons, Thomists tend to emphasize simultaneity in their explanations of causal series ordered per se, as I did in The Last Superstition.
But it is arguably possible at least in theory for there to be a per se causal series in which some of the members were not simultaneous. Suppose a “time gate” of the sort described in Robert Heinlein’s story “By His Bootstraps” were possible. Suppose further that here in 2010 you take a stick and put it halfway through the time gate, while the other half comes out in 3010 and pushes a stone. The motion of the stone and the motion of the hand are not simultaneous – they are separated by 1000 years – but we still have a causal series ordered per se insofar as the former motion depends essentially on the latter motion. I am not saying that this really is possible, mind you; it presupposes that time travel itself is at least possible in principle, which is controversial at best. But let’s grant it for the sake of argument. Insofar as the hand’s operation and existence will themselves presuppose various other factors, we have a continuation to the regress of causes ordered per se which cannot be ended until we reach a purely actual uncaused cause. The end result is the same, even if the statement of the argument needs to be made more complicated.
Now Hennessey, unlike Edwards, does see that it is the instrumental nature of the causes rather than their simultaneity that is doing the metaphysical work here. What Hennessey doesn’t see is that this completely undermines whatever force he thinks there is in Edwards’ critique. Edwards thinks that a series of causes in esse no more needs to have a first member than a series of causes in fieri does, and it is evident that he thinks this because he assumes that in the first sort of series no less than in the second, “every member is genuinely the cause of the one that follows it” (as Edwards puts it at the end of part III). Now if this assumption were correct, then it would indeed be odd for Aquinas to hold that a series of causes in fieri might be infinite while a series of causes in esse (or, better, a series of causes ordered per se) could not be. For it is precisely because they have their causal power independently of any earlier members of the series that Aquinas argues that the activity of the members of a per accidens series need not be traced to a first cause. So, if he thought that the members of a series of per se causes also had independent causal power, then his reason for tracing that sort of series to a first member would be undermined. But of course, that is not what Aquinas thinks. He thinks that they do not have such independent causal power, and so (contrary to what Edwards suggests) it is not at all odd, arbitrary, or unjustified for him to say that a series ordered per se needs to trace its activity to a first uncaused cause. Edwards misses this because he thinks that the Thomistic argument rests on an appeal to simultaneity, and Edwards doesn’t see how simultaneity requires an uncaused cause. But as I have said, the argument doesn’t rest on simultaneity as such. It rests on the instrumentality of the members of a causal series ordered per se, and instrumentality does require an uncaused cause.
[As a side note, this does not mean that there is no sense in which the members of a causal series ordered per se are genuine causes; Aquinas is not an occasionalist. But how his account avoids occasionalism is a separate issue, and does not affect the soundness of Thomistic cosmological arguments as such.]
It seems to me that the reason Hennessey misses this no less than Edwards is that he puts too narrow an interpretation on the word “first” in the expression “first cause.” He seems to think that what Aquinas was concerned to show is that if you lay out a series of causes ordered per se in a straight line, the line will necessarily have a beginning. But that is not what he was concerned to show. As Thomists sometimes point out, it wouldn’t change things in the least if we granted for the sake of argument that a series of causes ordered per se might loop around back on itself in a circle, or even that it might extend forward and backward infinitely. For the point is that as long as the members of such a circular or infinite chain of causes have no independent causal power of their own, there will have to be something outside the series which imparts to them their causal efficacy. (As the Thomist A. D. Sertillanges once put it, a paint brush can’t move itself even if it has a very long handle. And it still couldn’t move itself even if it had an infinitely long handle.) Moreover, if that which imparts causal power to the members of the circular or infinitely long series itself had no independent causal power, then it too would of necessity also require a principal cause of its own, relative to which it is an instrument. This explanatory regress cannot possibly terminate in anything other than something which has absolutely independent causal power, which can cause or “actualize” without itself having to be actualized in any way, and only what is purely actual can fit the bill.
That is the way in which it is “first” – first in the sense of being metaphysically ultimate or fundamental, and not (necessarily) in the sense of standing at the head of some (temporal or even non-temporal) queue. That is also why, contrary to what Edwards and so many other atheists suppose, it makes no sense to ask why fundamental physical particles or the like might not be the first cause. Particles and other “naturalistic” candidates for the ground floor level of reality are all compounds of act and potency, form and matter, essence and existence; accordingly, they are in need of actualization and are therefore necessarily less than the “pure act” or Subsistent Being Itself which alone could, even in principle, be that which causes without in any way being caused (or, as I would prefer to say, which actualizes potency without itself being actualized).
For those who are interested, I discuss these issues at greater length in Aquinas, which provides a more thorough, in-depth, and “academic” treatment of the Thomistic arguments for God’s existence than The Last Superstition does. (And without the jokes, polemics, or conservative political asides that some readers – including Hennessey – feel they could live without. But Hennessey does say some kind things about The Last Superstition and about this blog, for which I thank him.)