In a recent blog post, Edward Feser outlines a problem he sees with Rob Koons’ usage of relative actuality/potentiality to explain how an Aristotelian B-theorist might explain the reality of change. If you want to see Koons’ proposal then take a look at section 6 of his paper or take a look at Feser’s brief summary of it on his blog post; I will assume a general familiarity with it in this post. The objection is as follows:

Suppose someone suggested that time was nothing more than a spatial dimension.  I reject this view, and Rob wants to avoid it too.  One problem with it is that it also seems incompatible with the existence of real potentialities in the world.  If past, present, and future events are equally real in exactly the same way that the spatially separated hot and cold ends of a fireplace poker are (to borrow a famous example from McTaggart), then it seems that they are equally actual, just as the hot and cold ends of the poker are equally actual.  There is no real potentiality in a spatialized conception of time, and thus no real change — and thus, really, no time either.

But suppose our imagined spatializer of time defended his view by saying that there is potentiality of at least a relative sort on his conception of time.  Suppose he appealed to the poker analogy, and suggested that we could say that relative to the left side of the poker, the poker was actually cold but potentially hot, whereas relative to the right side, it was actually hot and potentially cold.  Suppose he suggested that there was therefore a kind of “change” in the poker from left to right.  And suppose he suggested that a similar kind of relative actuality and potentiality could be attributed to things and events at his spatialized points of time, and that a similar kind of change could therefore be attributed to them too.

In my view this would be clearly fallacious, involving little more than a pun on the word “change.” … I imagine Rob might agree, since, as I say, he too wants to avoid spatializing time, or at least denies that the B-theory need be interpreted as spatializing it.  But I fail to see how Rob’s notion of relative actuality and potentiality captures real potentiality, and thus real change, any more than my imagined spatializer of time does.

Feser’s point here is that the relativization of actuality/potentiality doesn’t help the spatializer to account for change, and he struggles to see how it could be comparatively any better for Koons. But I think he misdiagnoses the problem with the spatializer’s suggestion, and in fixing the diagnosis the difference between the spatializer and the Aristotelian B-theorist becomes clear.

As the last sentence of the quote makes clear, Feser thinks that the problem with the spatializer’s account lies in the fact that there are no real potentials anywhere, and so there can be no real change. But in the poker example, there surely are real potentials in the picture: the cold end is actually cold and potentially hot, whereas the hot end is actually hot and potentially cold. Anyone who accepts the Aristotelian account of change will affirm this, since we all know that pokers can change from hot to cold and back again. And they will likewise tell you can’t deny the presence of potentials simply because of the presence of actualities. Thus, if we suppose that time is spatially spread out like the poker, then the mere fact that all events are actual doesn’t prevent them from including various real potentials. Moreover, these real potentials and actualities seem to be adequately demarcated by using the notions of relative actuality and potentiality, so the problem isn’t there either.

The true problem with the spatializer’s answer is not that there are no real potentials, but that the potentials and the actualities are not connected in such a way so as to constitute change. Change, after all, is the actualization of a potential, it is not the spatial coincidence of a potential with an actuality. We can think of it like this: one reason someone might spatialize time is in order to explain why time is extended rather than collapsing into a single moment — it is extended, they say, for the same reason that space is extended, whatever that reason happens to be. But, of course, the extension of space doesn’t depend on the actualization of potentials, and therefore we know that simply pointing at spatially separated potentials and actualities doesn’t give us real instances of change. The problem, then, is that the spatializer spatializes time, and in doing so removes the possibility of an actuality ever being the actualization of a potential.

By contrast, the Aristotelian B-theorist need not spatialize time in order to explain its extension, because they have a ready alternative: the extension of time is explained by the actualizations of potentials. That is, the fundamental reason why things exist through multiple moments is that at earlier moments they have potentials which are actualized in order to bring about later moments. Of course, we’ve explained before that this is only the beginning of the account, since things can also move through time because of their real relations to other things. But even after we fill out all the details, the extension of time will always ultimately be explained with reference to the actualization of potentials — which, you will notice, is another way of stating the Aristotelian position that time is the measure of change.

So, then, the difference between the Aristotelian B-theorist and the spatializing B-theorist is that the former accounts for the extension of time in terms of the actualizations of potentials, whereas the latter has no room for the actualization of potentials because of how they account for the extension of time.