The Self-Refuting Logic of Arminianism

Anti-Calvinists often resort to a circular definition of predestination: God foreknew who would believe, and predestined those people.

However, there is a serious flaw in that argument, even beyond circularity.

If God knew it in advance, then their conversion was predetermined. Predetermined by what? Not by the will of the person, who wasn't born, yet. Not predetermined by God, the Arminian claims. That leaves what other options? Another god? Satan?

The logic of the Arminian cannot avoid predeterminism. It is only GOD's predetermination that the Arminian rejects. Isn't that unbelief?