I found a classical incompatibilist argument that looks that this:
If a person acts of her own free will, then she could have done otherwise
If determinism is true, no one can do otherwise than one does.
Therefore, if determinism is true, one cannot act of her own free will.
This argument seems sound to me, but I still don't feel like I'm convinced. Is there any way to reject this argument? In premise 2, for example, how exactly does the truth of determinism entail that one cannot do otherwise than what she does? Also, in refuting incompatibilism, does it imply that I have to be a compatibilist in doing so?