The argument for incompatibilism is really very simple.
1) I am not responsible for the eternal decrees of God (or the laws of nature and the condition of the universe at the big bang).
2) I am not responsible for the fact that, given the decrees of God, I sinned at 2 PM yesterday.
3) Therefore, I am not responsible for the fact that I sinned at 2 PM yesterday.
Not Responsible for A
Not Responsible for If A then B.
Therefore, Not Responsible for B.
How can I be responsible for that which is the modus ponens consequence of that for which I am not responsible?
I don't know. It seems pretty easy to me. Easy. I promise God I'll meet him for lunch. Suppose that God is good enough at reading minds that he knows if I'll go back on the promise. If I were to go back on the promise, he'll zap me so that I instantaneously appear at our lunch date.
I am not responsible for God's conditional intention. That God has such a conditional intention entails I'll be at our lunch date (one way or another). God never zaps me and I arrive freely. I'm responsible for being there, but it's a modus ponens consequence of something I'm not responsible for. Am I wrong?