rege et regis institutione, in which he wrote, the philosophers and theologians agree, that the prince who seizes the state with force and arms, and with no legal right, no public, civic approval, may be killed by anyone and deprived of his life..." The Jesuistic casuistry developed a similar theory, criticized by Blaise Pascal in the Provincial Letters. Before them, the scholastic philosopher John of Salisbury also legitimised tyrannicide, under specific conditions, in the Policraticus, circa 1159. His theory was derived from his idea of the state as a political organism in which all the members cooperate actively in the realization of the common utility and justice. He held that when the ruler of this body politic behaves tyrannically, failing to perform his characteristic responsibilities, the other limbs and organs are bound by their duty to the public welfare and God to correct and, ultimately, to slay the tyrant. In 1408, the theologian Jean Petit used biblical examples to justify tyrannicide following the murder of Louis I, Duke of Orleans by Petit's patron John the Fearless, Duke of Burgundy. Petit's thesis was extensively discussed and eventually anathematized by the church at the Council of Constance. A Shone Treatise of Politike Power, written by John Ponet in 1556, argued that the people are custodians of natural and divine law, and that if governors and kings violated their trust, then they forfeited their power, whether they relinquished their positions voluntarily or whether they had to be removed forcefully. The Tenure of Kings and Magistrates by John Milton in 1649 also described the history of tyrannicide, and a defense of it when appropriate. Cambridge's David George has also argued that terrorism is a form of tyranny of which tyrannicide is a negation. Abraham Lincoln believed that assassinating a leader is morally justified when a people has suffered under a tyrant for an extended period of time and has exhausted all legal and peaceful means of ouster. History Throughout history, many leaders have died under the pretext of tyrannicide. Hipparchus, one of the last Greek leaders to use the title of "tyrant", was assassinated in 514 BC by Harmodius and Aristogeiton, the original tyrannicides. Since then "tyrant" has been a pejorative term, lacking objective criteria. Many rulers and heads of state have been considered tyrannical by their enemies but not by their supporters. For example, when John Wilkes Booth assassinated Abraham Lincoln in 1865,