Is this a decent argument (i.e. logical, sound)? If God exists, God is an omniscient, omnipotent, wholly good being If God is wholly good, God would want humans to posess free will If God is wholly good, God could endow humans with free will But, if any being is omniscient or all knowing, such a being would know human choices and actions before they are chosen Under such conditions, free will would only exist as an illusion or in the mind as the human perception of having free will; true free will would not exist because God or some other power has predecided all human choices Therefore, God, if God exists, cannot be both wholly good and omniscient Therefore, God does not exist

When we look at arguments, we have two broad questions in mind. One is whether the conclusion follows from the premises, whether or not the premises are true. The other is whether the premises are actually true. So with that in mind, let's turn to the argument.

It's often possible by restating premises and adding other premises that are assumed but not stated to make an argument valid even if it's not valid as stated. Your argument is more or less this, I think

If God exists, then necessarily God is perfectly good, knows all, and is all-powerful,
Suppose God exists.
Since God is all-powerful, God can give us free will.
Since God is perfectly good, God wants us to have free will.
God does anything God wants to do.
Therefore, we have free will.
Since God knows all, God knows what we are going to do before we do it.
If God knows what we're going to do before we do it, then we don't have free will.
Therefore, we don't have free will.
CONTRADICTION.
Therefore, God doesn't exist.

We could clean things up a little more, but I take it that's the gist of your argument and it's valid-ish as I've stated it. What should we say?

Well, let's suppose free will really is inconsistent with Divine foreknowledge. If that's right, God is certainly smart enough to figure it out. But in that case, it's a bit odd to suppose that God wants us to have free will. After all, the structure of reality doesn't allow it. So the premise about God wanting us to have free will isn't so obviously true.

But it's also not obviously true that if God knows what we're going to do before we do it, that means we aren't free. This issue is part of an old debate about "logical determinism" or, under one understanding, about fatalism. The idea is this: God may know what we're going to do but that doesn't mean God or anything else makes us do what we do. Compare: suppose I know what you are doing at this very moment. That doesn't mean you aren't doing it freely. But on one view of God's relation to the universe, God's knowledge of the whole shebang is like my knowledge of what's before my eyes. On this view, the whole of history is before God's eyes, so to speak, even if God isn't responsible for everything that happens.

Of course, there's room to argue about this. But here's a different view. Suppose that God is in time, and that the future is open: there aren't any facts now about at least some future possibilities. For example: there's no present fact about when some particular atom will decay. In that case, God doesn't know when the atom will decay. But that doesn't mean God isn't omniscient. If we think the future is open about some things, then there aren't any facts about those things for God to know. An omniscient being only knows what's actually there to be known.

So there are lots of ways to argue with your argument. Of course, that doesn't mean the argument is worthless; philosophical arguments are pretty generally the kinds of arguments that people can argue with.

One more thing, though. Even if your argument works, the most it shows is that the God of traditional theism doesn't exist. Showing that wouldn't be trivial. But it's not the only way to think about God and, for some people, not even the most interesting or attractive way.

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