In this paper, I show that Kant’s solution to the third antinomy is a reply sui generis to the consequence argument. If sound, the consequence argument yields that we are not morally responsible for our actions because our actions are not up to us. After expounding the modal version of the consequence argument advanced by Peter van Inwagen, I show that Kant accepts a key inference rule of the argument as well as a requirement of alternate possibilities for moral blame. (...) Kant must therefore reject one of the premises of the consequence argument to be able to deny its conclusion. Whereas Kantian altered-past compatibilism denies the premise of the consequence argument which states the fixity of the past, Kantian altered-law compatibilism denies the premise that states the fixity of the laws of nature. My analysis shows that Kantian altered-past and altered-law compatibilism are logically consistent, yet it also reveals that they depend on strong metaphysical premises. It must be investigated whether these premises withstand textual scrutiny and whether they are credible in their own right. By way of conclusion, I draw the outlines of this investigation. (shrink)