As some of you may know, I am presently editing a book by Gunther Laird calls The Unnecessary Science. Natural Law philosophy, about which I have talked a great deal recently, owes an awful lot to Aristotle, Aquinas and other thinkers from a bygone era. One of the cornerstones of this essentialist worldview is the pair of ideas of potentiality and actuality:
The concept of potentiality, in this context, generally refers to any “possibility” that a thing can be said to have. Aristotle did not consider all possibilities the same, and emphasized the importance of those that become real of their own accord when conditions are right and nothing stops them. Actuality, in contrast to potentiality, is the motion, change or activity that represents an exercise or fulfillment of a possibility, when a possibility becomes real in the fullest sense.
These concepts, in modified forms, remained very important into the Middle Ages, influencing the development of medieval theology in several ways. Going further into modern times, while the understanding of nature, and according to some interpretations deity, implied by the dichotomy lost importance, the terminology has found new uses, developing indirectly from the old….
In contrast, the position of Western Medieval (or Catholic) Christianity, can be found for example in the philosophy of Thomas Aquinas, who relied on Aristotle’s concept of entelechy, when he defined God as actus purus, pure act, actuality unmixed with potentiality. The existence of a truly distinct essence of God which is not actuality, is not generally accepted in Catholic Theology.
Laird expands on this idea:
What did Aristotle provide in response? The theory of actuality and potentiality. He believed that Parmenides was simply wrong to hold that the only alternative to “being” was “non-being.” Potentiality was another alternative, and one that could ground a much more workable metaphysical framework. Return again to our caterpillar: He exists as a hungry little worm-like creature, or, in other words, he is actually a caterpillar. Parmenides could see no way he could possibly be a butterfly, but Aristotle held that there was something that could influence our little friend despite not existing in the same sense at the same moment. Namely, the fact that the caterpillar was potentially a butterfly. For Aristotle, the ways anything potentially could be—caterpillars, coffee, rubber balls, whatever—occupy sort of a middle ground between existence and non-existence, which is how he could claim that existing things could change without asserting that change could come from non-existence or non-being.
Now, for Aristotle, there was no such thing as an “infinite” number of potentialities. Any actual thing—that is to say, anything that exists in some way or another—is potentially a certain number of ways and not others. So Mr. Caterpillar is potentially a butterfly, or, if he’s unlucky, potentially a meal for a hungry bird. But he is not potentially a dog or a rock or a philosopher. No matter what you do to him or how many leaves you feed him, when he makes his little chrysalis, a dog or a rock will never pop out, and he will never do any sort of philosophy, unless maybe if you ask Franz Kafka. The same applies to any other object in our experience. A cup of coffee might be actually hot and bitter, but it is potentially cool (if you leave it out for a while) and potentially sweet (if you put a lot of sugar into it). It is not potentially blood or radioactive fuel, because nothing you do to it will ever make it capable of conveying nutrients or powering a reactor. A red rubber ball (to use Feser’s favorite example) might be potentially blue (if you paint it) or squishy (if you hold it over a flame), but it has no potential to bounce to the moon or follow someone around by itself.
 FP, 18-19, SM, 32-33, TLS, 53-54.
He goes on to discuss this in more depth before saying:
Thomists claim we can’t have an “explanatory regress”—that is to say, we can’t just explain the laws of physics by referring to an even deeper law, which would require a deeper law, and so on, ad infinitum. For the purposes of argument and the interests of saving time, let’s say they’re right. So, given what we have discussed about the laws of physics potentially being different, thinkers like Aristotle, or more specifically, his successors (since everything we know about the laws of physics would only be discovered centuries later) would say they involve certain potentialities being actualized. What could possibly actualize those? It would have to be something that was “purely actual,” something with no potentialities at all. This “purely actual” thing would have to be eternal. It would never have come into existence, but would simply exist eternally and necessarily, since coming into being involves a potentiality being actualized (for instance, a butterfly comes into being because the nutrients in leaves actualize that potentiality in a caterpillar). It also couldn’t be changed at all, and would be entirely unchangeable, because change involves actualizing potentials, and anything with potentials wouldn’t be purely actual. It would also be omnipotent, because if it actualizes the laws of physics it must be able to exert control over them—like a flame or an electric coil exerts control over the temperature of a pot of coffee (or, more literally, the person who starts the fire or turns on the stove, since that actor would be actualizing the potential of the flammable materials or the electric coil). If such a being could control the laws of physics, it must be able to do just about anything—send a meteor to destroy a city by changing the laws of gravity for a bit, raining fire from the sky by momentarily changing the chemical circumstances under which flame is produced, and so on.
TLS, 96-97, FP, 30-33. Again, this isn’t exactly the argument Feser uses, but a very simplified one to illustrate his general line of reasoning. We’ll come back to this in much more depth when we discuss miracles in chapter 2.
There is much more I could quote and go on to quote, pertaining to these ideas. The differentiation between potentiality and actuality here appears to be a subtle ploy in order to shoehorn God into the equation. I did, however, want to bring up this point that perhaps invalidates the whole differentiation and categorisation of these two ideas.
First of all, I am a conceptual nominalist, as I have set out umpteen times, and this arguably eliminates such metaphysical contortions anyway by saying such mental categorisations are products entirely of the mind and have no ontic existence independent of the conceiving minds in question. Indeed, such nominalism, in my opinion, destroys the foundation upon which natural law, essentialism and Thomistic philosophy and theology is built.But let’s ignore that minor digression.
I want to look at potentiality and relate it to a deterministic or adequately deterministic framework. I would argue that such frameworks equally eliminate the idea of potentiality; or, at least, make potential synonymous with “the future”.
Let’s talk about this caterpillar. The caterpillar, it is of a particular species and genus. It has a genetic blueprint. In other words, it will only turn into a certain type of butterfly. Given the environment it is actually born into and given the conditions of the food it eats and the chrysalis it makes, it will invariably turn out in a particular way, with a particular colouration and of a particular science. When we talk about potential, I think we are smuggling in a very human conception about what could be in a very general sense.
This butterfly could be of this particular colouration or that particular colouration, it could be of this size, or that size. We line up all the theoretical futures that this butterfly could have given that we don’t know the initial conditions with our limited human minds. However, if we knew every single condition down to every single wave function of the world, then we could predict with surety what the outcome would be.
If I was to say I’m going to toss a coin, we might both agree that it could potentially flip as a head or as a tail. However, if I was to understand every single initial condition and every single variable at play, on the flip of that coin in that particular instantiation of a coin flip, then actually (pun intended), I would know what the outcome of the coin flip would be. There would literally be no potential head or potential tail but there would be an actual future coin flip of head (for example). I keep coming back to this idea that any contextualized thing really doesn’t have the potentiality to be anything other than the exact thing it will be deterministically caused to become, taking into account the causal circumstance it finds itself in.
Thus to talk about “Pure Act” and other notions that depend upon this differentiation of potentiality and actuality is somewhat meaningless.
Of course, we could get onto a debate about causal determinism and the influence of quantum indeterminacy, if indeed it exists. But given this, my criticism would obtain.
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