Both Newton and Einstein claim that nature is simple and that simplicity is an epistemic guide to truth. This chapter examines various arguments for these claims, including that, historically, simpler theories have been more empirically successful than complex ones; that the epistemic value of simplicity can be demonstrated by appeal to Bayes’s probability theorem; and that simpler strategies for changing one’s beliefs in the light of new evidence can be shown to be more successful than complex ones. It is concluded that none of these arguments shows that nature is simple or that simplicity is an epistemic virtue.