But worse than that, and the point of this thread, is the incompatibility of libertarian free will with divine (or any) foreknowledge.
We'll see. You could start by precisely defining "freedom", "will" and "knowledge", because it's obvious from what follows that you have no well-defined concepts in mind but only murky ideas wallowing in numerous metaphysical presuppositions and choices to use the words in apparent senses that beg the question.
To have free will, X and ~X both have to be possible.
Your first blunder. There's no logical implication that my ability to freely will to do something depends upon the possibility of my being able to do it. You just made this up. It is sufficient, for me to will something, that the willed "act" be cognitively meaningful, that is, it needs to be a purely logical "possibility", but it doesn't need to be possible in a contingent sense: I can't will to "construct a square circle" because "square circle" is a nonsensical pairing of words and there is no object of my will as a result; however, I can very well will to sprout wings and fly like a bird, despite it being an impossibility contingent upon nature, and there is no basis upon which to assert that the fact of this impossibility means I can't have willed this freely.
The underlying confusion here is apparently in an equivocation of two distinct meanings of "freedom", namely, of "freedom" that is impinged upon by the existence of boundaries with "freedom" that is impinged upon by determinism. "Freedom of the will", as used in metaphysical discourse, is referring to the latter kind of freedom, and while you could only have had the former in mind, knowlingly or not, in this part of your argument, you freely switch between the two concepts whenever you need to, resulting in one long fallacy of equivocation.
Yawn.
Now if God knows I will do X, then doing ~X is only a perceived possibility, not an actual one.
Firstly, you haven't demonstrated this, only asserted it; indeed, you haven't even defined the distinction between a "perceived" and "actual" possibility.
Secondly, it doesn't follow from this what I haven't willed freely.
Finally: God knows that I will do X because I choose to do X and he is transcendent. If my doing "~X" (this is a nonsensical use of logical connectives, but be that as it may) is only a "perceived possibility", then that is because my of MY choice to do X. That God knows this by virtue of His transcendence IN NO MANNER IMPINGES UPON THE CAUSAL PROCESS BY VIRTUE OF THIS KNOWLEDGE ALONE.
If it were actual, then it would be possible to change God's foreknowledge, which is absurd.
I'd say that's a non sequitur, but then again, you have not defined "actual possibility", so it's difficult to say.
One more time for you: GOD'S FOREKNOWLEDGE OF AN ACT CANNNOT EO IPSO IMPINGE UPON THE ONTOLOGY OF THAT ACT - THAT is absurd. What power does foreknowledge in-and-of itself have over the causal structure of that act? What causal influence does it have that it could annihilate ones free choice in a matter? (of course there is a hidden mechanstic assumption in such arguments which regards foreknowledge as possible only due to events being predetermined - but this is question begging, and it has nothing to do with foreknowledge that is a result of transcendence or of scientia media)
There isn't any sound argument of the form "I can't have freely chosen X because God foreknew this".
But then I don't have free will, since doing ~X is not possible.
Addressed in the first part.
This is number one bullshit, in the words of a wrestler from Dagestan.
Some may try to escape this by saying "if you chose ~X, God's foreknowledge would have been different."
I don't need to "escape" this because it's utterly inconsequential to freedom of will.
Be that as it may ...
This is a slimy non-answer.
No, it's a perfectly legitimate answer.
The world where you do ~X is a different world, in which case doing X would be impossible, for in that world too, you can't change what God foreknows.
The foreknowledge is in place before, during, and after the decision. So any appeal to "would have" is irrelevant: it's not going to be different from what it in fact is.
The foreknowledge is only "in place before, during, and after the decision" because of the decision. What part of this do you not understand? I make a FREE choice IN TIME, and that choice is therefore DETERMINED ETERNALLY outside of time, regardless of whether there is a God or there is not, and God, being transcendent, therefore has "foreknowledge" of the act. You are committing a category error in placing in approachign that foreknowledge from a temporal perspective instead of from a transcendent one.
I think the Free Will Defense fails for multiple reasons. I think the notion of free will is incoherent.
I think the notion of causation is incoherent without reference to the power of free agents as an analogue. See David Hume for where that leads to.
Your will operates on the calculations made by the intellect.
The intellect cannot operate without acts of will, indeed, it is regularly invoked by an act of will. If you want to talk about a "regress", there you have one: the intellect prompting the will to prompt the intellect to be used.
The intellect perceives something as desirable, and the will acts on it. To put it simply: you do what you desire.
Simply bullshit. I regularly ignore what I "desire" or do its exact opposite: it's called being a human being, not an automaton.
You can't choose what you desire,
I can and do, Q.E.D.. An assertion to counter an assertion.
But it's obvious we have here the second equivocation: confusion of "desire" as a purpose to which I will to direct myself, as a positive judgment of my intellect which may or may not become such an object fo my will, and as motions of the body and soul over which may or may not become objects of intellection, judgment and will - depending upon my choices.
and even when it seems you can, that "choice" would be random or based on what you desire to desire
No, that choice would be an act of my free will - see how easy this is?
What do you mean by "random"? More to the point, since you insist upon determinsim, please define what it means for something to be determined and how this happens. Please explain what a "cause" is and how "causes" determine their "effects" - please don't beg the question or appeal to the existence of mathematical formulae which describe mechanicla actions but can't account for why they do.
For my part, I have the analogue of my willing as an immediate object of my experience by which to account for such concepts, but you, placing the cart before the horse and at least implicitly asserting that this experience is illusory, have no such basis.
-- and this leads to a regress.
Only because you're begging the question through a bunch metaphysical presuppositions.
That evident in your "regress" - it's because there is a MECHANISTIC assumption underlying your entire discourse, which can conceive of no DETERMINED processes but mechancial ones and therefore regards the question like "what caused the will to choose x" to be a demonstration fo an infinite "regress" in the concept of freedom of will. No, RANDOMNESS (however you actually define it) is not the only possible UNCAUSED phenomenon: the choices of the will themselves are also UNCAUSED. You, of course, deny this, but you deny it implicitly in the hidden assumptions udnerlying your attempted proof that "free will" is "incoherent". Such sophistry only impresses the faithless.
Adam sinned because he desired to, and you can't choose what you want.
You sin because you freely choose to and you will be held accountable to the Ancient of Days for it at the end of time, oh idolater of your own deeply flawed intellect.
Mental illness. That is what the denial of the PHENOMENOLOGICAL FACT, self-evident to the subject, of his own free agency would be if any of the "intellectuals" who denied it actually LIVED as though they believed their own bullshit. But, of course, none of them take their own assertions seriosuly enough to live by them. Yes, yes, ye olde reductionism. Ye olde denial of the experience of the subject in favour of a theoretical world constructed by his intellect. Sights, sounds, emotion, nothing is real except except some abstract world I can write down in equations on a piece of paper. I experience my existence as an I, an existential subject, who is free, but so what: that theoretical world is more real than the self-evidently real - it's the "true" one.
But what's the point of arguing? I'm just an automaton.
No God would allow children to starve, get beaten, the Holocaust, and many other sufferings.
And you know this because ... human beings have magical intrinsic value in as cosmic accidents in a godless world, which you then project upon a world in which your idea of "God" would exist in order to state what he would or would not do? Sure. "Evil" doesn't exist in a godless world, yet here you are appealing to its existence to demonstrate that God doesn't have any ... pat yourself on the back, why dontcha?
To the contrary, I say: humans are vile, disgusting creatures, who deserve much worse than they get, and the fact that this world which utterly rejects Him is a lot less bad than it ought to be is the surest sign that God IS benevolent and merciful: God may be "omnibenevolent", but one first has to define that term and determine where and to whom such "benevolence" would "rightly" apply - it's semantics. I don't truck with sophists. Q.E.D.
I'll leave it to you amateur "philosophers" to squabble it out - I have better things to do with my time than argue with a "future-theist" who thinks that OUR ideas are "absurd".