The usage of excommunication goes back to the early history of Islam for the extreme Kharijite sect declared for the first time all other Muslims who did not agree with them as apostates and killed them brutally in the 7th century. The extreme mentality of the Kharijites has been witnessed in various extreme sects throughout Islamic history. More recently, Justice and Development Party (the AKP), the political Islamists of Turkey, has been using the concept of takfir (excommunication) against its opponents. In this essay, we will examine the concepts of faith (īmān) and disbelief (kufr) and then attempt to analyze the ruling AKP"s usage of excommunication (takfīr) on the basis of primary Islamic sources. The essay will seek the relation between the takfir and extremism as well as its connection with violence and terrorism by examining the ideology of the ruling AKP in Turkey.