It is no secret that causality places a central role in natural theology. That is to say, the notion of causality is central to arguments—mostly cosmological arguments—that attempt to prove the existence of God. It is because of this fact that most theologians work very hard to ground the principle of causality as an absolute. For if the principle of causality has exceptions, then natural theology will take a hit. Hence it is obvious that theologians have a vested interest in preserving the immutability of this principle. Because of this fact some, then, will claim that theists are extremely tendentious when it comes to talk of causality, and that such talk should be challenged, and put under the skeptical magnifying glass. I completely agree with this, though I do believe that the “skeptics” or non-theists can be charged with a bias as well (can’t we all?) since a denial of the principle of causality is central to their position, all things being equal.I will not attempt to distance myself from the aforementioned theologian. I agree that the principle of causality is something that, perhaps through my own biases and wishful thinking, I am determined to defend. That being said, however, I do in fact believe that said principle is hard to deny, and I do believe that any attempt to do just that will run into absurdity and incoherence; And thus, my belief in the principle of causality is at least surely grounded in reason, and has just warrant.
It is my objective in this post to demonstrate why it has said warrant.So, let me begin by articulating the principle of causality. The principle of causality states that whatever is moved from potentiality (potency) to actuality (act) is done so by something already actual. (Let the reader understand that the potentiality of a substance is just the potential that the substance could realize, and the actuality of a substance is just the way it currently is realized—that is, the way it currently exists or exhibits being. For instance, an acorn is actually an acorn and is potentially an oak tree, while it is not potentially a lizard.) Another way to formulate the principle is to say that whatever is changed is changed by another, since change just involves a reduction of some potency of a thing to an actualization of said potency. Thus, the glass of water on my table has the potential to be knocked over (among other things) but this potential can only become a reality--that is, it can only be actualized--if, for example, someone or something (actual) knocks it over.
Now, while one can conjure up all sorts of examples that satisfy the principle of causality, how do we know that this principle is an actual principle in the sense that it holds immutably, without exception? Well, to one who tries to deny the principle, there are only two other options: 1) a potential can actualize itself, or 2) nothing can actualize the potential. Obviously 1) is not possible because potency qua potency cannot do anything because it is not actual. In fact, the only way for it to actualize itself would be for it be actual before it is actual, which is a contradiction and an absurdity. Now, 2) is likewise absurd because nothing is, well, nothing, and nothing cannot do anything. Nothing is not actual and cannot act on anything, precisely because it is nothing--that is, because it is the absence of being. So, then by logical necessity we can see that that which is moved from potency to act must be done so by something already actual.
Another formulation of the principle of causality is that whatever begins to exist has a cause. And again, we can see that this formulation is necessarily valid. For if something comes into being, then there are only two options left over if one is to deny the principle: 1) the substance caused itself to come into being, or 2) the substance came into being from nothing. It should be obvious that these options fail for the same reasons as above. 1) is false because in order for a thing to be self-caused it would have to exist before it existed in order to cause itself to exist, which is incoherent. 2) is false because nothing cannot be a cause because nothing cannot do anything, since it is by definition the absence of anything. Thus, this formulation of the principle of causality is also necessarily valid.
So far then we have seen that the principle of causality is a metaphysically absolute principle. There simply is no logical room for any exception to said principle, for any alternative runs into absurdity and incoherence. It seems then that we can be completely certain of the validity of the principle of causality.