Recently, Scott Clark rescued an anti-Molinist quote by Voetius from the brink of oblivion.
From the points which have been so far upheld against middle knowledge it is clear that the whole difficulty in the present controversy reduces to this one point: Could free conditioned things, from eternity indifferent by nature to futurition or nonfuturition, have passed over into the state of a future event otherwise than by the divine decree? This is the fundamental of fundamentals, on which the whole weight of the case rests. This is that postulate, which both we cannot concede to our adversaries and they cannot prove to us. …Middle knowledge is effective and congruous for any end by its nature. Upon it God is forced to wait in the wise framing of His decrees, which are bound to have a fixed result. The truth or falsity of future conditioned free ones is not known from their causes or from the divine decree, but from the actual occurrence of the thing. Before every act of His will God can see certainty in things quite uncertain by their nature. In short, there is an ens independent of the supreme ens.” (See Heppe’s Reformed Dogmatics, 80ff.). (link)
Voetius’ question is a bit ambiguous. In Molinism, God’s decree comes after middle knowledge but before free knowledge. So it’s not true that anything has ‘passed over into a state of a future event’ prior to God’s decree.
But perhaps Voetius is asking if God’s decree isn’t what determines what free creatures will do, what does? The answer is of course God’s free creatures. God has freedom to choose this or that and He has given us a limited amount of freedom as well.
On the other hand, perhaps Voetius’ is asking about counterfactuals of freedom. Logically prior to God’s middle knowledge, we can choose this or that, but it is not true that we would choose this over that. When we get to middle knowledge, it is true that we would choose this over that. How does it become true apart from a divine decree? The answer is that statements about what we would choose do not become true. In natural knowledge (the moment logically prior to middle knowledge in which God knows everything that can happen) what we would do under this or that circumstance is not taken into consideration at all. It’s not as if counterfactual statements are untrue in natural knowledge and change into being true in middle knowledge. Rather, in natural knowledge, there are no counterfactual statements at all; true or otherwise. In middle knowledge, statements about what we would do in this or that circumstance, are either true or false.
Finally, Voetius says freewill amounts to something existing apart from God’s supreme existence (ens). But this overlooks both God’s concurrence and the distinction between exercise and specification. It overlooks God’s concurrence, in which God upholds the existence of the effects of secondary causes. It overlooks the distinction between exercise and specification, in that God determines that we choose and we determine what we choose.