The Islamic State if Iraq and al-Sham's (ISIS) ideology and tactics in Iraq and Syria continue to be rejected by all people of conscience. Numerous Muslim scholars and political leaders have strongly condemned its ideological claims and terrorist acts. An international alliance of Muslim and Western countries has been bombing ISIS targets in Iraq and Syria. Yet ISIS continues to make advances and remains a matter of controversy. Why?There are two main arguments – religious and political – against ISIS. The religious argument, as attested to by numerous condemnations by prominent religious authorities, de-legitimizes and undermines ISIS's claim to religious authenticity and legal basis. Western commentators and political leaders ask Muslim countries to be vocal against ISIS's claims to religious authority and urge them to take a clear position against its xenophobic calls. As a matter of fact, Muslim scholars and leaders have taken a clear stance against ISIS. A couple of examples below show the extent to which religious authorities have clearly undermined ISIS's claim to religious legitimacy and legal justification for its acts of "takfir" or ex-communication, which ISIS uses to justify the killing of Sunni and Shiite Muslims as well as Christians and others. The religious argument against ISIS has also rejected its claim of establishing an Islamic caliphate – a self-proclaimed political kingdom that serves the interests of ISIS ideologues rather than the principles and values of Islam.While the religious argument has been firmly made against ISIS, the political argument has gone missing. The political circumstances that have prepared the ground for ISIS's rise are largely ignored to cover up the failure of the international system of establishing peace, justice and equality. ISIS will not be defeated religiously and/or politically without addressing the colossal political failures in Iraq and Syria, not to mention the other sources of political grievances and resentments in Palestine, Egypt, Libya and elsewhere.An authoritative religious argument has been made against ISIS by a group of prominent Muslim scholars, jurists and intellectuals in an open letter to Abu Bakr al-Baghdadi, the leader of ISIS. The letter, whose full text can be found here clearly demonstrates that "it is forbidden in Islam to issue fatwas without all the necessary learning requirement ... to oversimplify shariah matters and ignore established Islamic sciences … to kill the innocent … to kill emissaries, ambassadors, and diplomats … journalists and aid workers." It also states that "it is forbidden in Islam to declare people non-Muslim unless he [or she] openly declares disbelief … to harm or mistreat – in any way – Christians or any 'People of the Scripture' … to force people to convert … [and] to torture people." While all these acts are banned by Islamic law, it is also forbidden "to declare a caliphate without consensus from all Muslims."These principles are shared by all the major schools of Islamic law. And they have been accepted and stated by such institutions as the Organization of Islamic Cooperation (OIC), which represents 1.4 billion Muslims in 57 countries. The OIC has "condemned [ISIS's] persecution of Christians and other religious minorities in Iraq," saying the "forced deportation under the threat of execution" is a "crime that cannot be tolerated." On July 22, Mehmet Görmez, the head of the Directorate of the Religious Affairs in Turkey, referring to ISIS's declaration of the caliphate, said that "such declarations have no legitimacy whatsoever." Görmez also added, "The statement made against Christians is truly awful. Islamic scholars need to focus on this [because] an inability to peacefully sustain other faiths and cultures heralds the collapse of a civilization," in an interview with Reuters. In Egypt, the grand mufti of Al-Azhar University, Shawki Allam, while rejecting ISIS's terrorist acts, said, "[ISIS] gives an opportunity for those who seek to harm us, to destroy us and interfere in our affairs with the [pretext of a] call to fight terrorism," in The Daily Star.Numerous scholars and community leaders from Europe and the U.S. have also rejected and condemned ISIStarget="_blank"'>