Ibn Taymiyyah disagreed with his master. To live freely and justly as Muslims required a leader committed to Islamic guidance, he argued. If that leader failed in his duty to uphold Muslim principles and did not abide by Islamic law, then he was not really a Muslim but a kafir; his rule was invalid. Ibn Taymiyyah declared that it was incumbent upon all Muslims under the rule of an impious leader to rebel. Employing the practice of takfir, he even went so far as to argue that any Muslim who was willing to abide by the rule of the kafir leader was himself a kafir.
