 Finally, a further challenge to Kvanvig’s treatment of knowledge and understanding focuses on his claims regarding epistemic luck, and in particular, his insistence that luck cases show how understanding and propositional knowledge come apart from one another. In order to bring the luck-based challenge into focus, we can distinguish three kinds of views about the relationship between understanding and epistemic luck that are found in the literature: strong compatibilism (e.g., Kvanvig 2003; Rohwer 2014), moderate compatibilism (e.g., Pritchard 2010a: ch. 4) and incompatibilism (e.g., Grimm 2006; Sliwa 2015). Strong compatibilism is the view that understanding is compatible with the varieties of epistemic luck that are generally taken to undermine propositional knowledge. In particular, incompatibilists maintain that understanding is undermined by neither (i) the kind of luck that features in traditional Gettier-style cases (1963) cases, nor with (ii) purely ‘environmental luck (e.g., Pritchard 2005) of the sort that features in ‘fake barn’ cases (e.g., Goldman 1979) where the fact that one’s belief could easily be incorrect is a matter of being in an inhospitable epistemic environment. Moderate compatibilism, by contrast, maintains that while understanding is like propositional knowledge in that it is incompatible with the kind of luck that features in traditional Gettier cases, it is nonetheless compatible with environmental epistemic luck. Incompatibilism rejects that either kind of epistemic luck case demonstrates that understanding and propositional knowledge come apart, and so maintains that understanding is incompatible with epistemic luck to the same extent that propositional knowledge is.