This is an argument to which I was introduced recently. It claims that Molinism entails some kind of determinism. Let's see if it does!
“Let's introduce the shorthand operator @=“In all possible worlds that have our same past up to time T.” We then have:
1. @, if God foreknows x, then x will happen.
2. @, God foreknows x.
3. Therefore, @, x will happen.
We don't need to argue that x will happen in all possible worlds, only in all possible worlds that share our past. No determinist (who is not also a fatalist or necessitarianist) would argue that what happens does so necessarily, only that it must happen *given the past*. As this is the case with molinism, molinism entails determinism.”
(1), as it stands, is false. Why? Because not all of these possible worlds contained in @ are actual, and thus the locution “will happen” is false for all of these non-actual worlds. The same thing goes for “foreknowledge.” On the Molinist account, “foreknowledge” and “will” statements are known to God’s free knowledge, not middle. In that sense, God does determine something. Namely, God determines the truth of the actual world. What do I mean by that? Let’s take a look at this proposition:
P1. Socrates does not exist in the actual world.
Pre-volitionally, as it relates to God, is (P1) true or false? Well, that all depends, doesn’t it? On what does it depend? On which world is actual, of course! So on propositions that reference “the actual world,” the world which God selects determines whether that proposition is true. Since God selected our world, call it W, (P1) is false. But had God selected another world, say, W’, and in W’ Socrates never existed, then (P1) would have been true. Now, while it is true that (P1) can be “world-indexed” to read:
P1’. Socrates does not exist in W.
P1’. Socrates does not exist in W.
It remains obvious that (P1) and (P1’) are not identical premises (since we can discern the above difference). As such, God determines these propositions, as well as tensed truths such as “will” locutions. What’s our role in this? Simple. Our role depends on what our creaturely essences would do were they to be in a fully specified set of circumstances (taken in a maximal way as a possible world). That is to say, God won’t be able to determine some truths because, as it so happens, the creaturely essences (persons) required to perform specific acts freely would not do so in those circumstances. So we can see the whole argument above is muddled.
But perhaps we can repair it to get a stronger version against Molinism (I suppose we shall employ “The Plantingian Strategy,” so named for Alvin Plantinga, who famously strengthens arguments against his position only to demolish them like a house of cards). Perhaps we could say something like the following: @=“In all possible worlds.” We then have:
1’. @, if God foreknows x, then x will happen.
2’. @, God foreknows x.
3’. Therefore, @, x will happen.
Well, the argument seems obviously valid. But is it sound? That is, can we say that all of the premises are true? We could charitably interpret (1’) as stating that for every world W, if God knows x is true in W, then x happens in W. This is unobjectionable. But what of (2’)? Is it saying that “in all possible worlds, God knows some particular x is true of these worlds”? If so, it both renders the argument invalid and no Molinist would accept it. So perhaps (2’) means something like, “For every world W, God knows any particular proposition belonging to W is true.” But then all that follows in (3’) is that “For every world W, any particular proposition x happens in W.” But this is more a tautological truth; a necessary world-indexed proposition that is equivalent to:
P2. Every true proposition in W is true in W.
So the re-formulated argument won’t work here either. So let’s re-work it one more time, taking into account the objector’s goals. @=“In all possible worlds that have our same past up to time T.” We then have:
1”. @, if God knows x, then x will happen.
2”. @, God knows x.
3”. Therefore, @, x will happen.
Let us say that “x” stands for a CCF (Counterfactual of Creaturely Freedom). So the idea we want to preserve by (1”) is that if God knows that in all possible worlds which share our same history up to a particular time T agent S would freely do A, then agent S would freely do A in all of those possible worlds. God does know that in all of these possible worlds that share our same exact history, S would freely do A at T. Therefore, agent S would freely do A in all of those possible worlds.
Now why should we think “Molinism entails determinism” from (1”-3”)? It’s not clear. Apparently, the objector doesn’t want to argue that these happen in all possible worlds, or even all possible worlds in which we exist. Just all possible worlds which share our same past. But what kind of “determinism” is this, then, anyway? It certainly doesn’t appear to be causal determinism. Why do I say that? Two reasons: 1. This argument leaves open the door that we do otherwise than what we do, in potentially countless possible worlds (unless he is prepared to argue we exist only in worlds that share our identical past up to any particular time, in which case we may as well say we only exist in one possible world [since for any world posited and at any time we can construe worlds to be identical in a maximal sense, and by the indiscernibility of identicals, these worlds would be one and the same]). But that means we have the ability to do other than what we would do, which is perfectly consistent with libertarian free will (LFW). 2. Causal determinism is that the initial conditions of the universe, coupled with antecedent events, entail (hence “causal”) the content of CCFs. Thus, it is said, LFW is inconsistent with causal determinism.
But the argument steadfastly denies this entailment, since he says he’s not a “necessitarian.” But of course, that’s just what entailment is; the necessity of the whole of events. But suppose he would agree that the necessity is over the whole; it is necessary that if the premises are true, the conclusion is true. Now on naturalism, I would agree it’s hard to see how the will is free. Given that I’m not a naturalist, however, I don’t see that it’s the initial conditions and antecedent events that cause my LFW response in the content of the CCF. It’s just not an entailment relation.
Take this, for example:
P3. If it is raining, then I wear a jacket.
Who should think that I mean an entailment relation by (P3)? Yet who would on that basis claim (P3) is false? Suppose I have always taken a jacket when it rains, without fail. Who wants to argue that this is because I was caused to do so, instead of just because I am diligent? Perhaps some people do, but no one who takes on LFW. In any case, I fail to see what’s causal about this.
Finally, some people admit Molinism does not entail causal determinism, but still “determinism” nonetheless. What does this mean? It’s never been quite clear to me. What is this determinism, and why should this count against the Molinist? In any case, I don’t think these types of objections succeed, especially since they are typically so ambiguous.
 It should probably be noted that this formulation makes God superfluous—if any agent whatsoever actually knows “x is true in W,” then it follows by the definition of “know” that “x is true in W.”