The First Two Critiques - The Great Breakthrough

Kant says we can't know whether we're free because one of the entinemies of pure reason is are we free or are we... Everything determined. He thinks it's just undecidable through pure reason, you can't prove both things. And so I think the great breakthrough of the second critique is that he says I actually can... I think that we prove that we're free. So his idea is that we wouldn't have come up with the possibility of doing one thing or the other if we didn't have that if it wasn't actually possible.