Why The Primary Cause Must Be Pure Actuality (and Non-Composite)
While something can be *a* primary cause in one causal series while having potencies with respect to another causal series, this cannot be the case for that which is *the* primary cause of the existence of things. I’ve covered this objection before (including in my eBook How to Think About God; also, brief sketch here), but since it is commonly overlooked, the conclusion is worth revisiting.
Background: By primary cause I mean something which has (or can produce) the relevant causal property considered in a causal series *in virtue of what it is*, and is thereby ultimately responsible for the initiation/possibility of the series itself. So, for example, when looking for a primary cause in, say, a collection of mirrors reflecting light (with light being the causal property under consideration), we cannot explain the light solely by the mirrors or their arrangement, since mirrors do not possess the relevant causal property inherently, but only derivatively. Mirrors can reflect light, but mirrors do not produce light. For that, we must ultimately arrive at a flashlight, say. Also, notice it doesn’t matter how many mirrors there are; even if there were an infinite number of mirrors reflecting light, the light itself would not – in fact, could not – be explained without arriving at some primary, fundamental cause which possess the ability to produce light essentially; i.e. in virtue of what it is. What I am here getting at is the famous “per se,” “essentially ordered,” or “hierarchical” causal series which Aquinas is known for deploying in his arguments for God; that is, a sort of causal series which, even if they could proceed to infinity in some sense, would not remove the need for a primary/fundamental cause to make intelligible/possible the series altogether.
Back to the original point. One objection to the Thomistic position that God must be pure actuality (and therefore non-composite; possessed of no potentiality, etc) is that there could be a primary cause which is still a composite of act/potency, and, so why must God be pure actuality and non-composite? What makes Him so special?
So, to be clear, the objection is not attacking the act/potency distinction, nor denying that anything which reduces from potency to act requires that which is already actual (causal principle). The objection is simply trying to dodge the conclusion that that which is the primary cause of the existence of things must be purely actual, and thereby trying to escape the conclusion of classical theism, which follows from pure actuality.
And, indeed, there are causal series where something is, in fact, a primary cause of some relevant property, but not non-composite with respect to act/potency. The sun, for example, with respect to light reflecting from the moon. The moon itself (like mirrors in the previous example) does not produce light, but merely has the potential to reflect (and once again, even if we had an infinite number of moons, we’d still need at least one sun/star to get the series of reflections started). But the sun is obviously not non-composite, since the sun stands in potency to other actions, including supernova. Thus, the objector contends, you can have a primary cause of some causal property which is non-composite.
Yes. Granted. However, that has not only never been denied, but is made obvious from the stock examples typically given to illustrate the nature of a per se (or essentially ordered) causal series, whether of the hand pushing the stick pushing the stone, the chandelier suspended from a chain, light reflecting from mirrors or moons, etc. The purpose of the stock examples is not to demonstrate the non-compositeness of the primary cause, only that a specific type of casual series must have a fundamental/primary cause for its very possibility. So, the objection misses the point with respect to that which is the primary cause of the existence of things (which would itself be *the* primary cause, period), because once that sort of primary member is considered – more specifically, once the causal property under consideration is existence itself – relevant differences enter in which rule out the possibility of compositeness within the primary cause; and more specifically ruling out the possibility of the primary cause standing in potency to something.
So, let us grant (since this isn’t what’s under objection) that there is that in which essence and existence are not distinct, or, to put it differently, some primary cause of the existence of things (existence now being the causal property under consideration); something which not only just is existence itself, but is ultimately responsible for imparting existence to anything else which exists, at any moment which it exists, especially since, as Thomists argue, there is, and can only be, one such thing whose essence just is existence itself. (Again, see How to Think About God for arguments.)
At this point, however, there are only two options if we wish to say this fundamental cause of the existence of things is a composite of act/potency. First option: it has some potency (some potential for existence) which is yet, but could, be actualized. But if this is the case, there will then be – in fact, must be – some more fundamental (already actual) aspect which actualizes, or at least could actualize, such a potency, in which case, the potential wasn’t really a part at all, but rather merely an effect which arose from the more fundamental (and already actual) reality. So, that option is out; for it simply failed to trace the causal regress back far enough. Because whatever else such a potency could be, it cannot, we must remember, be a potency unless there is some more fundamental actuality to cause it, and no matter how many times we run a similar thought experiment, we will keep being drawn ineluctably back to that which is pure actuality itself to either explain the potency or its ultimate actualization. And that purely actual reality will be *the* primary cause, properly considered.
Alternatively, if we say there is just a potential part which is not, nor ever could, be actualized, then we are talking about literally nothing, since any potential which is not, nor ever could, be actualized is not a potential, since to be a potential implies something which at least could be actualized. This second alternative then is just a trick of language and amounts to no real alternative at all.
So, whereas the first proposed alternative does not trace the causal sequence far back enough and the second option upon deeper analysis is nonsense, there really is no sense to be made of a primary cause of the existence of things that is not purely – and fully – actual.
Furthermore, the objection misses the point (especially from Thomists) as well, that if there is such a thing that is pure actuality, whose essence just is existence itself, and thereby exists of necessity, it will be utterly unique – one and only one. So, it shouldn’t surprise us that we see other causal series with a primary cause of some other causal property that is not non-composite; in fact, we should expect exactly that given that there is, and can only be, one ultimate, non-composite cause of the existence of things; thus, everything else will, by default, be composite; thus, even if some composite entity stands as a primary cause of some causal property in an essentially ordered hierarchical series, this is neither a threat to the arguments for God, nor surprising.
Finally, a brief quote from Gaven Kerr, which summarizes the same conclusion from a different perspective: “An effect stands in potency to some cause, and the cause actuates he potency of the effect in that respect. Hence if we have a composite of act and potency, its potency has been actuated in some way, in which case it has been caused.” So, while act-potency composites may be *a* primary cause in some respects, an act-potency cause cannot be *the* primary cause in the final respect: the order of existence.
Related Podcast
Philosophy Friday: Arguing Essence and Existence with Dr. Gaven Kerr