Among that select band of philosophers who have managed to change the world, and not just to interpret it, it would be hard to find a pair with a higher public profile than Brutus and Cassius — brothers-in-law, fellow-assassins, and Shakespearian heroes. Yet curiously little is understood of the connection, if any, between the fact that they were philosophers and their joint decision to form the conspiracy against Caesar. It may not even be widely known that they were philosophers.
What work has been done on this question has been focused on Cassius' Epicureanism, thanks above all to a famous review published by Momigliano in 1941 which included a seminal survey of the evidence for politicized Epicureans. I shall myself have less to say on that topic than on the richer, and less explored, evidence for Brutus. For the present, we may note that at the time of the assassination, March 44 B.C., Cassius had been an Epicurean for just three or four years; that he had already prior to that been actively engaged in philosophy; but that his previous allegiance is unknown. His conversion to Epicureanism seems to have been timed to reflect his decision in 48 B.C. to withdraw from the republican struggle and to acquiesce in Caesar's rule, expressing his hopes for peace and his revulsion from civil bloodshed. This sounds in tune with a familiar Epicurean policy: minimal political involvement, along with approval of any form of government that provides peaceful conditions. We may, therefore, plausibly link Cassius' withdrawal to his new-found Epicureanism. In which case it becomes less likely that his subsequent resumption of the political initiative in fomenting conspiracy against Caesar was itself dictated purely by his Epicureanism. Yet he did remain an Epicurean to the end.6 At its weakest then, the question which we must address might simply be how, when he became convinced that Caesar must be eliminated, he managed to reconcile that decision with his Epicureanism. I shall have a suggestion to make about Cassius' Epicurean justification, but it will emerge incidentally during the examination of the evidence for Brutus, who is the real hero of this paper.