Is Molinism truly compatible with the idea of persons in other possible worlds? Can it really be possible that there is a counterfactual truth about me such that “If I were born in the 18th century, I would have sided with the American colonials against the British”?
So, here, a lot depends on one’s theory of personal identity, as well as what counts for discerning modal truths. I personally hold to at least a basic rundown of Plantinga’s theory of creaturely essences, where there is an abstraction that is “composed of” all and only essential properties, including world-indexed properties (of course, this is the abstract description; my concrete theory of personal identity is that we are immaterial souls). So, Socrates in our world is the concrete instantiation of the abstraction who had this “maximal property”–call it “Socraeity”–and he had these properties de dicto (“about what is said”) due to the abstraction, but de re (“about the thing”) due to his own choices. These include counterfactuals.
Now consider that there is a truth of the matter of the following counterfactual (at least if it is not counterpossible):
(S) If Socrates had been born in 20th-century Athens, then he would not have been killed.
Now what if someone advocates for a kind of origin essentialism, which is a doctrine that teaches one’s origin cannot be significantly different than what it was in order to retain personal identity (I use “retain” in a colloquial sense, as no thing loses its identity in favor of something else)? Is S still possibly true? Accounts of origin essentialism always or nearly always rely on the idea of physical transmission of genetic material, and so rely on one’s parents being the same. If this is right, the claim may go, then such a counterfactual about Socrates is a counterpossible, and does not have a non-trivial truth-value. While I’m not sure about origin essentialism, I think we can grant it and still achieve the desired original result. After all, God presumably could have made it the case that Socrates’ parents were a special creation, formed of the appropriately relevant genetic material and information–or that Socrates himself was.
But then if this is so, then it follows that all sorts of counterfactuals about Socrates are true, both in our world and many others. But then it follows that there are many world-indexed properties that correspond to these true counterfactuals, and these world-indexed properties help jointly (with all other essential properties of Socrates) to constitute Socraeity. So then it follows that if such counterfactuals were descriptive of actual states of affairs, then Socrates would be who he is.
I also think that we should be interpreted as saying something like, “It is possible that the set of true counterfactuals could have turned out such that [fill in counterfactual under consideration].” It may be part of the set of true counterfactuals or not; we have no way of knowing. However, most people take real modal logical possibility to be had in cases where the concept or state of affairs under consideration is articulated without self-contradiction or violation of a necessary truth that rules it out. There doesn’t seem to be anything about the example provided that is self-contradictory, and I think the preceding suggests we don’t have a necessary truth sufficient to rule it out. So while, for all we know, S is a false counterfactual, the set of true counterfactuals could have turned out to be different than what it was, and in those related worlds (presumably not Lewis-like nearby worlds, at least not nearby enough)–worlds where a different set of counterfactuals is true–such a counterfactual as S may be true. This also suggests that it is at least possible, for all we know, that one exists in worlds sufficiently removed from the true set of counterfactuals (not precisely difficult); this sense of existence is in an abstract sense, not concrete.
Plantinga does believe we are immaterial souls; this is the concrete particular of the abstraction that is the creaturely essence. I hesitate to call them universals, only because this raises the potentially controversial issue of multiple instantiability.
It looks like it’s at least possible that Socraeity, for example, has as part of its set the property being killed in 21st century Athens at time t in world W-146. This could be so on either an A or B-theory. On a B-theory, time is a block, and so located at that particular point on the particular block belonging to the world W-146 could potentially be that counterfactual. On an A-theory, that property can be held, since there doesn’t seem to be anything that precludes the mere possibility of world W-146 (its feasibility is another issue entirely). And if this is the case, then Socraeity can include time-indexed counterfactual properties (properties that we have about counterfactual scenarios), where the times are radically different. And I mean “can” in the mere sense of logical possibility, which is, of course, not the same as feasibility.
Thus, my conclusion is that Molinism will work with potentially true counterfactuals about individual persons in various worlds that differ even radically from this one.