Tyrannicide is the killing or assassination of a tyrant or unjust ruler, purportedly for the common good,[1] and usually by one of the tyrant's subjects.[2] Tyrannicide was legally permitted and encouraged in the Classical period. Often, the term tyrant was a justification for political murders by their rivals, but in some exceptional cases students of Platonic philosophy risked their lives against tyrants. The killing of Clearchus of Heraclea by a cohort led by his own court philosopher is considered a sincere tyrannicide.