In this essay I discuss the role of Cassius' philosophical beliefs in his decision to assassinate Caesar. I analyse the situation of Cassius and discuss whether or not Epicureanism can justify the assassination, then I use these conclusions to establish the importance of Epicureanism in Cassius’ decision. I take the relevant aspects of Epicurean philosophy (privacy, friendship, fear, stability and justice) separately and make a judgement as to what parts of Epicureanism encourage or discourage the assassination. I bring this together with a discussion of how each of these aspects contributes to the Epicurean goal of tranquillity and thus assess whether the assassination is the correct course of action for an Epicurean. I conclude that, though some aspects of Epicureanism would encourage Cassius to murder Caesar, the assassination is still unjustifiable due to both the personal and political beliefs of Epicureanism. I further conclude that Cassius held Epicureanism as a theoretical ideology, whilst holding his Republican beliefs as more practical in application. Overall this shows that Cassius political beliefs were more important than his philosophical allegiances in these decisions; this gives weight to Griffin’s theory that Greek philosophy’s role in Roman politics was more theoretical than practical.