Thursday, February 27, 2020
Agere sequitur esse and the First Way
Aquinas’s First Way is also known as the argument from motion to an Unmoved Mover. The most natural way to read it is as an argument to the effect that things could not change at any given moment if there were no divine cause keeping the change going. But some Thomists have read it instead as an argument to the effect that changing things could not even exist at any given moment if there were no divine cause keeping them in being. That’s the reading I propose in my book and my ACPQ article and it’s a line of argument I develop and defend in greater depth in chapter 1 of .
On my way of presenting the argument, it begins with change, not because this is the phenomenon the argument is ultimately most concerned to explain, but rather because it provides the clearest way to introduce the distinction between actuality and potentiality. Change entails the actualization of potential, but so too does the sheer existence of a thing at any moment. The latter is what the argument, as I present it, is ultimately most concerned with. But it is much easier for most readers to get an initial handle on the concept of the actualization of potential by considering change than it is by considering the existence of a thing at a moment.
Now, does that mean that at the end of the day, a divine cause really explains at most only the existence of a thing at a time, and that this cause does not after all explain change? Should we say that God merely keeps things in existence but that, for all Aquinas can show, their changes require no divine explanation?
No, that doesn’t follow, and it isn’t true. Recall the principle agere sequitur esse or “action follows being,” which I defend and deploy in Five Proofs (and which I’ve had occasion to discuss in and in ). As I’ve argued there and elsewhere, the principle, together with other considerations raised by arguments like the argument from motion, entails a concurrentist account of God’s relationship to the world. Given that action follows being – that the way a thing operates reflects its mode of existing – we can conclude that a thing would have no causal efficacy at all without God’s cooperation or concurrence with its activity, just as a pen could not write without your cooperation or concurrence with it (by holding and moving it). For if a thing could act or operate apart from God’s action, then since the way a thing acts reflects its mode of being, it could also exist apart from God’s action. And that is ruled out by arguments like the argument from motion, developed the way I develop it. (See Five Proofs for the details of this defense of concurrentism.)
Since change always involves a potential being actualized by some efficient cause, change too, and not merely the existence of things, thus requires a divine cause (to cooperate or concur with the efficient cause). The overall picture is therefore much like that of what I characterized above as the first and more natural reading of the First Way. But the line of argumentation is less direct. It isn’t a straight shot from the reality of change to the conclusion that the Unmoved Mover must keep change going. It’s rather an argument from the sheer existence of things to the conclusion that the Unmoved Mover must keep them in existence, and then a combination of this result with the principle agere sequitur esse to yield the further result that the activity of things, and thus their bringing about of change, requires divine concurrence.
That’s not to say that the more direct sort of argument is not correct. It’s just that that’s not the sort of argument I’ve been the most interested in defending.
Here’s another observation. Aristotle’s own version of the argument from motion to an Unmoved Mover is often interpreted as an explanation precisely of change rather than the existence of things. The idea (on this interpretation) is that Aristotle thinks an Unmoved Mover is necessary in order to account for why the world continues to change from moment to moment, but he does not take the sheer being of the world from moment to moment to require such an explanation. (I put to one side the question of whether this is a correct interpretation of Aristotle.)
The principle agere sequitur esse would arguably afford a path even from this version of the Unmoved Mover argument to the conclusion of the version I defend. If action follows being, then if change – and thus the action of things in the world – requires an explanation in terms of a divine cause, then the sheer being of things must require such an explanation too. For if things could exist apart from such a cause, why couldn’t they act apart from it?
If this is correct, then the three dimensions of our discussion – the being of a thing, the action of a thing, and the link between being and action enshrined in the principle agere sequitur esse – are thus so tightly interconnected that the differences between interpretations of the argument from motion may be moot. We can reason from the being of things to the existence of an Unmoved Mover, and the principle agere sequitur esse will then tell us that the action of those things too requires the Unmoved Mover. Or we can reason from the action of things to the existence of an Unmoved Mover, and the principle agere sequitur esse will then tell us that the being of those things too requires the Unmoved Mover. We end up at the same place, by neighboring routes.