Tuesday, April 23, 2019
Aristotelians ought to be presentists
Presentism holds that within the temporal domain, only the present exists and the past and future do not. Alex Pruss thinks that . That would be news to Aristotle, Aquinas, and other presentist Aristotelians. I agree with them rather than with Alex, and I think that presentism is in fact the natural view to take if one starts with an Aristotelian view of the nature of physical reality, and of the nature of time in particular. I spell all this out at length in . Here I will just try briefly to convey the general idea.
Remember that change, for the Aristotelian, entails the actualization of potential. For example, when a green banana ripens and turns yellow, the banana’s potential to be yellow is actualized, and when it later begins to rot and turns brown, its potential to be brown is actualized. Now, time, for the Aristotelian, is just the measure of change with respect to succession. When we say that it took a week for a banana to ripen and then rot, we are measuring the rate at which these changes succeeded one another. Time thus piggybacks on change.
Hence, the material world is a temporal world precisely because it is a changeable world. For the Aristotelian, matter just is, fundamentally, the potentiality for form, and change is the actualization of that potentiality – matter’s taking on new forms which supplant the ones that had been there before. Time actually passes only insofar as this supplanting occurs. Because God is pure actuality without potentiality, his mode of existence is strictly eternal or timeless rather than temporal.
Angels occupy a strange middle ground. Because they are immaterial, angels are, unlike physical objects, imperishable. They have no matter that can lose substantial form, which is what happens when a physical substance perishes. So, being immaterial, they are not in time. Still, angels, like us, have to be created, and they can exhibit something analogous to change of a mental sort. Hence they are not eternal either. This middle ground between temporality and eternity is called aeviternity.
Now, suppose God creates a physical universe with only a single thing in it, an unripe green banana. Suppose that he does so in such a way that its natural tendencies are miraculously suspended. For example, it does not begin to ripen. It is changeable, but its potentialities are not actualized, so that there is in fact no change.
For this reason, there is also no passage of time in this imagined world. Hence there are no past or future events. Is there a present? Surely there is, because since this is a material world, we are not talking about eternity and we are not talking about aeviternity. We are talking about the third alternative, a temporal world. It’s just a world in which time has been suspended – precisely because change has been suspended – rather than being altogether atemporal. It’s now in this world, even if what is now never becomes past. It is for that reason a presentist world, since the present exists and past and future do not.
Now suppose instead that change is not suspended and the banana begins to ripen. It goes from green to yellow. What that means is that it has lost its greenness and gained yellowness, and that in turn boils down to its no longer being merely potentially yellow but instead actually yellow, and its no longer being actually green. And if the process continues until the banana rots, the banana will eventually actualize its potential to be brown. In this case we have the passage of time.
While the banana is still yellow, though, does the future, brown state of the banana exist? Of course not, because the brownness is at this point still in the banana only potentially, not actually. The future state of the banana no more exists in this scenario than it did on the first scenario, in which change was suspended. There being change, and thus temporal passage, on this second scenario in no way suffices to make it true that future things and events exist. They will exist, but until the potentialities are actualized, they do not.
But what about the past, such as the banana’s being green? Does that exist after the banana has turned yellow? How could it? After the banana has turned yellow, its greenness is at that point no longer actual, any more than the brownness is actual. Hence the greenness no more exists than the brownness does. The greenness did exist, just as the brownness will exist. But neither does exist. The past, like the future, no more exists on this scenario than it did in the first scenario, in which change had been suspended. So on this scenario too, we have a presentist world. But the actual world is in all relevant respects like this second scenario. It’s just that there are a lot more things in the actual world than a single banana. So the actual world is a presentist world.
Now, so far I have left only implicit a further, key element of the Aristotelian view of time, and making it explicit will help make it clear where the illusion that past and future events exist comes from. Remember that I said that time is the measure of change with respect to succession. But who is doing the measuring? The answer is that the mind does the measuring. There is a sense, then, in which time is mind-dependent. The qualifier “in a sense” is crucial, however, because the Aristotelian view of time is not an idealist one.
The best way to understand it is to think of it on analogy with the Aristotelian position on universals. For the Aristotelian, a universal like triangularity does not exist as a Platonic Form, in a third realm distinct from concrete individuals on the one hand and minds on the other. It exists only as abstracted by the mind from concrete individual triangles. At the same time, it is not a free creation of the mind. Triangularity is really there in the concrete individual triangles, but just mixed in with their individualizing features, as it were, rather than existing there qua universal. The Aristotelian view is not Platonist, but it is not nominalist either.
Now, where time is concerned, the Aristotelian rejects the idealist view that time is entirely a creation of the mind, just as he rejects the nominalist view that universals are free creations of the mind. But neither does the Aristotelian accept the idea that time exists as a kind of substance in its own right, entirely apart from the world of changing things, as the Newtonian absolutist does. That, for the Aristotelian, would be comparable to the Platonic error of regarding universals as substances in their own right, occupying their own distinctive realm. To speak of time as if it existed entirely apart from change and apart from the minds that measure change is like speaking of triangularity as if it were a Platonic Form that existed entirely apart from all concrete individual triangles and all minds.
One thing that can happen when we start to Platonize time in this way is that we take the units in terms of which the mind measures change – seconds, minutes, hours, days, months, years, and so on – and we reify them. For example, we start talking about last month, or about the year 1947, as if it were some entity that we have in some way moved past, and of next month, and the year 2047, as if they too were entities, but ones that we haven’t arrived at yet. We , as we do when we talk about the Form of Triangularity.
This is exacerbated by the tendency in physics to confuse mathematical models of physical reality with physical reality itself. Especially since space too tends in physics to be represented in a highly abstract mathematical way, the highly abstract mathematical representation of time that physics works with facilitates thinking of time as space-like, which further aggravates the tendency to think of all moments of time as in some way equally real. From the Aristotelian point of view, these are all just variations on the same Platonizing error. The B-theory of time, speculations about the possibility of time travel, and other exotica familiar from the contemporary philosophy of time literature have diverse philosophical motivations – including philosophical motivations disguised as scientific ones – but a major part of the story is this basic error (as the Aristotelian sees it) of reifying abstractions. (Again, these points are all developed at length in Aristotle’s Revenge.)
Let me now turn, then, to Alex Pruss’s objection. Alex writes:
A foundational commitment of Aristotelian philosophy is that all facts are grounded in what substances and features intrinsic to substances, namely forms and accidents, exist. But it is possible for the past to have been different without there being any difference in what substances and features intrinsic to substances presently exist. Therefore, the Aristotelian cannot equate present existence with existence.
In other words, Aristotelians cannot escape the standard grounding arguments against presentism.
End quote. What he has in mind by “the standard grounding arguments against presentism” are arguments like the and the , which I have addressed in my recent exchanges with Bill Vallicella.
Now, Alex is right that the Aristotelian grounds facts in existing substances and features of substances. But he errs in assuming that this thesis simply must be read in a way that would pose problems for the presentist. That Aristotelians like Aristotle and Aquinas were themselves presentists should make that obvious enough. There are facts about the White House and there are facts about the north tower of the old World Trade Center, whereas there are not, in the same sense, facts about Stark Tower (from the Marvel comics and movies). The reason is that the White House does exist and the north tower of the World Trade Center did exist, whereas Stark Tower is purely fictional.
What the Aristotelian thesis that Alex cites is intended to rule out are views that deny the ontologically fundamental status of substances, as well as idealism, relativism, and other views that might be taken to deny the reality of ordinary material substances. Presentism fully respects such concerns. Again, there really was a north tower of the old World Trade Center, even though it no longer exists. We needn’t somehow translate that statement into a statement about what exists now, or what exists in some tenseless way, in order to capture the relevant point. The fact that the tower did exist is sufficient to respect the Aristotelian concern to ground all facts in reality.
Nothing more need be said, it seems to me, to reconcile the Aristotelian’s presentism with his concern to ground all facts in real substances and their features. If someone has a problem with this reconciliation, I submit that it is not Aristotelianism that is the source of the worry, but some other philosophical commitment.