Compatibilist libertarianism claims that alternate possibilities for action at the agential level are consistent with determinism at the physical level. Unlike traditional compatibilism about alternate possibilities, involving conditional or dispositional accounts of the ability to act, compatibilist libertarianism offers us unqualified modalities at the agential level, consistent with physical determinism, a potentially big advance. However, I argue that the account runs up against two problems. Firstly, the way in which the agential modalities are generated talks past the worries of the (...) incompatibilist in the traditional free will problem. As such, it fails to dispel the worries that determinism generates for the incompatibilist. Secondly, in spite of the ingenious use of the supervenience thesis and multiple realizability, the position still allows us to generate the old worry that determinism at the physical level would mean no alternate possibilities at the level of agency. In particular, I develop a new example, the ‘atomic slit case’ that demonstrates how physical level information is salient to what is possible at the agential level, motivating incompatibilism. (shrink)