Somebody sent me this argument earlier today:
1. Libertarian free will is incoherent.
2. If LFW is incoherent, then God does not have LFW.
3. If God does not have LFW, God’s actions are either determined or random.
4. If God’s actions are determined, then modal collapse obtains.
5. If God’s actions are random, God is not in control of His actions.
6. If God exists, then modal collapse does not obtain.
7. If God exists, then God is in control of His actions.
8. God does not exist.
At first blush I thought the argument showed promise. If logically valid, it could either be made into a good argument against the existence of God, or, if one begins with the assumption (for other reasons) that God exists, it seems to show that premise 1 must be denied, thus Calvinists would have to stop appealing to arguments for premise 1 for Reformed soteriology, on pain of no longer being theists at all (to say nothing of orthodox).
However, closer examination shows that this argument is, even though strictly ‘logically valid’ in form, very obviously flawed even if interpreted charitably. Notice that premise 4 moves from God’s actions being determined rather than (libertarian) free, to modal collapse. This move is illegitimate though, since the consequent obviously doesn’t follow from the antecedent. Modal collapse obtains if and only if there is no non-vacuous distinction between contingent facts and necessary truths. However, God could clearly be determined to create a universe in which indeterministic events occurred – imagine he had to create a world in which Quantum Mechanical events really were the sorts of events which the Copenhagen interpretation of them suggests, and where these events instantiated. If such events were indeterministic, and not necessary, they would seem to be contingent (notice that even if they are brute they are contingent, and at least not necessary). Therefore, the argument moves too fast from determinism in God’s case, to modal collapse.
The argument’s use, if it has any, must be to show either that 1) a particular conception of God and/or theological doctrine of God and man must be wrong, or that 2) that particular conception of God and/or theological doctrine of God and man must be strongly bound up with libertarianism. Even the Calvinist may think twice about affirming the first premise given what seems to follow. Indeed, it seems to be not beyond question whether if God’s actions are determined he is really in control of them in any relevant sense. Generally Calvinists will agree that God has libertarian free will, though, so they should, at least most of them, already be poised to reject the first premise.
Alternatively the Calvinist might just embrace modal collapse and give up all talk of ‘contingent’ ‘possible’ ‘brute’ or ‘necessary’ facts. Or at least, perhaps, the Calvinist will call all modal discourse a ‘useful’ convention, and as such a language better suited to doing science than doing logic (just speculating here).