Virtue epistemology and epistemic twin earth

A popular form of virtue epistemology - defended by such figures as Ernest Sosa, Linda Zagzebski and John Greco - holds that knowledge can be exclusively understood in virtue-theoretic terms. In particular, it holds that there isn't any need for an additional epistemic condition to deal with the problem posed by knowledge-undermining epistemic luck. It is argued that the sustainability of such a proposal is called into question by the possibility of epistemic twin earth cases. In particular, it is argued that such cases demonstrate the need for virtue-theoretic accounts of knowledge to appeal to an independent epistemic condition which excludes knowledge-undermining epistemic luck.