Here are some half-baked thoughts on the relationship between actualism and presentism. It is not clear whether actualism entails presentism. It is clear, however, that if actualism entails presentism, (coupled with a few other, less controversial assumptions), some interesting implications follow.
For the presentist, talk of objects that did or will exist parallels the misleading modal talk of possible objects that do not exist. Just as there are no possible but nonexistent objects for the actualist, there are no non-present entities or objects for the presentist. There are only objects that exist at present. Tense, like actuality, therefore, is a real and monumentally significant feature of ontology. So according to the actualist, if God were to take an inventory of the total contents of reality using as his criteria everything that a totally unrestricted existential quantifier “∃x” ranges over, the only things that would turn up on his list would be things that exist. No possible but nonexistent entities or objects would turn up. Similarly for the presentist; if if God were to make an inventory of all that exists, the only things that would show up would be things that presently exist, or exist now. No non-present entities or objects would be catalogued. So an interesting question is How, at least from a presentist perspective, the items catalogued in God’s actualist inventory differ from his presentist inventory.
Presentists believe that some propositions are essentially tensed. This fact also caused Plantinga to revise his initial account of possible worlds from maximal temporally-invariant (i.e., tenseless) states of affairs to “a temporally variant state of affairs that is maximal with respect to temporally invariant states of affairs.”[1] This is because Plantinga believes states of affairs, an hence possible worlds, are isomorphic to propositions. If possible worlds are isomorphic to propositions, and certain propositions are essentially tensed, then at least a subset of the propositions that make up a possible world must also be essentially tensed. In a striking passage, Plantinga gives a glimpse of this revised conception of a possible world as quite congenial to a presentist ontology:
There are many propositions, I believe, whose truth value varies over time. Thus the proposition Paul is typing is true at the present time, but fortunately not at every time. As I see it, a sentence like ‘Paul is typing’ uttered at a time t does not express the temporally invariant proposition Paul types at t but a temporally variant proposition true at just the times Paul types. Since states of affairs are isomorphic to propositions, there are also temporally variant states of affairs—Paul’s typing, for example. But this makes trouble for the above account of possible worlds. A possible world, I said is maximal; since Paul is in fact typing, α, the actual world, includes Paul’s typing. But then α itself will be temporally variant and will be actual only as long as Paul types. In fact, of course, its actuality will be briefer. Just now a bird is flying towards my window: name that bird ‘Sylvester.’ Let t be the present time; for each time t* as close as you like to t, Sylvester is a different distance from me. α, therefore, will be actual for no more than an instant.[2]
Here, it’s almost as if what is actual (contingently, at least), for Plantinga, just is what is what is present at t. But, as soon as t ceases to be present at some later time, say, t’ becomes present, so α ceases to be actual and α’ becomes actual. The actual world is actual as long as the present is present. Consider the following diagram, where each time t corresponds to some temporally variant (i.e., present) state of affairs that is maximal with respect to the temporally invariant states of affairs α* (e.g., the state of affairs consisting in 1+1 being 2, etc.):
While it is tempting to think of “the actual world” as the set composed of each temporally variant state of affairs {αt1, αt2, αt3, αt4,…} plus α*, this not correct. The actual world, on this picture, is represented in toto by any one pair α*+αt1, α*+αt2,α*+αt3, etc. This is because the temporally variant state of affairs that is actual at αt1 ceases to be actual at αt2, etc. Thus, for the actualist, temporal and modal operators are analogous. Just as the actualist prohibits moving from “dragons exists in W” to “dragons exist,” the actualist will also prohibit going from “JFK exists in α*+αt” to “JFK exists,” which is precisely what presentists maintain.[3] Indeed, many presentists, when pressed about what “is present” means, will insist that it just means “exists” or “is real.” F. M. Christensen, for example, says that “to be present is simply to be, to exist, and to be present at a given time is just to exist at that time—no less and no more.”[4] Actualism, or so it seems, entails presentism.[5]
Here is a second line of thought that might go from actualism to presentism. The problem giving rise to actualism was the conanical view’s implying there are, or could be, things that do not exist, or merely possible objects. Notice that this problem seems to be exclusively about contingent objects—objects, like dragons—that do not exist in the actual world, but do exist in other possible worlds. Merely possible objects, as they’re called. As such, the problem is not about necessary objects, like numbers or other abstract objects, which do exist in the actual world and every other, and moreover could not have not existed in the actual world or any other. Now, I wonder how closely connected contingent objects are with a temporal mode of existence. Do contingent objects have an essentially temporal character to them? Paradigm cases of a contingent property is one that an object exemplifies at some time t but does not exemplify at some other time t*. So contingent objects could be those that exist at some time t but do not exist at some other time t*. If this is right, then what the actualist really says is that there are no, nor could there have been, contingent things that do not exist, where “exist” is contingent, temporal existence. t and t* are analogous to, if not coextensive with, the times at which a different actual world obtains. But to affirm that there are no temporal things that do not exist is to affirm presentism. So, if contingent existence is essentially a temporal mode of existence, then actualism entails presentism.[6]
This same issue comes up in a slightly different way. As several philosophers have noted, the problem of possible but nonexistent objects is precicely parallel to the problem of temporal but non-present properties prosed by McTaggart’s paradox as follows. The canonical view seems to entail that an object can have the mutually exclusive properties of being actual and being merely possible: some contingent object that exists in the actual world, say, you or I, are actual in the actual and are merely possible in worlds in which we do not exist. But how can something be both actual and merely possible? Actualism avoids this denying that there are any such things as merely possible objects. The same problem can be raised against the concept of intrinsic change. If every object is identical to itself, how can an object exemplify a property at t and another property at t* and still be the same object? The presentist responds by denying that the object possesses only the properties it presently has. The same object did have some property p at t, but now has p* at t*. There are no exemplified properties that are not presently exemplified. William Lane Craig, quoting Robin Le Poidevin, concisely summarizes:
Now actualism is precisely parallel to presentism. As Le Poidevin admits, “the doctrine that only the actual world is real avoids the modal paradox just as the doctrine that only the present is real avoids McTaggart’s paradox.”* Since these two problems and their solutions are parallel, consistence demands that they must be accepted or rejected together. Either accept both actualism and presentism or else hold that just as all moments of time are equally real, so all possible worlds are equally real.[7]
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*Le Poidevin, Change, Cause, and Contradiction, p. 35.
The solutions to the “modal paradox” and McTaggart’s paradox are, therefore, are actualsim and presentism, respectively. Actualism and presentism, at least as solutions to these problems, are parallel in the same way that, say, parodies of the ontological argument are parallel to their parodied versions: like love and marriage, you can’t have one without the other. This seems like something less than actualism entailing presentism just as such, though.
According to the foregoing analysis, then, the following seems initially plausible:
(1) If actualism is true then presentism is true.
Now suppose we adopt the perspective of someone who is attracted to a robust ontology of possible worlds. Couple (1) with a few other, less controversial assumptions:
(2) Either actualism is true or concretism is true.[8]
(3) If the tenseless theory of time is true then presentism is false.
From these three assumptions, some really interesting implications follow:
(4) If presentism is false then actualism is false.
(5) If the tenseless theory is time is true then actualism is false.
(6) If actualism is false then concretism is true.
(7) If the tenseless theory of time is true concretism is true.[9]
These implications, with the exception of (6), are as interesting as they are puzzling. Implications (4) and (5) seem so jarring that they might even be seen as more obviously false than (1) itself. Furthermore, although the tenseless theory of time is widely embraced by philosophers and scientists alike, hardly anyone at all embraces concretism. Many think it is just absurd (hence, the “incredulous stare”). Thus, this argument could be seen by many, if sound, to be a reductio (of sorts) against the static theory of time.
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