I can't find the exact article, but it goes along these lines..
This is your argument, right?
- God knows choice "C" that a human would claim to "make freely".
- It is now necessary that C.
- If it is now necessary that C, then C cannot be otherwise (this is the definition of “necessary”). That is, there are no actual "possibilities" due to predestination.
- If you cannot do otherwise when you act, you do not act freely (Principle of Alternate Possibilities)
- Therefore, when you do an act, you will not do it freely.
It is wrong, due to a modal fallacy.
In particular, the argument assumes that if C is true, it becomes necessary for C to be true, which is incorrect as C is contingent. Otherwise, one can argue that the future is set already regardless of his actions.
Modal_logic
Well, I find modal logic to be problematic in many ways, including the difficulties with 'possible world' ontology. In general, the distinction between 'necessary' and 'contingent' events gives me hives.
So, there are two options: either there is only one possible world (and so one future at each point) and ALL events are necessary.
OR
There is more than one possible world and, in fact, more than one possible future at several points. In this case, a choice determines which future a person finds themselves in. And, in this case, the God of your argument would know that *if* a certain choice was made, then the person would find themselves in a particular possible world, but there would still be several possible futures at some points and thereby knowledge of which choice is made is impossible (since there is a possible world for each choice).
So, while this is close to my argument in many ways, it is NOT my argument. I say that knowledge implies necessity at that point. So, if an event is known 'outside of time', then it *is* necessary.