Converting the Hagia Sophia to a mosque is not only an affront to the religious sentiment of millions of Christians. It does not only violate Turkey’s obligations to the international community, for a global monument that has functioned as a museum since 1935, protected by UNESCO as a world heritage site. Nor does it only draw a wedge between Islam and Christianity, reinforcing Turkey’s international isolation. It also stands as an assault against the founding principles of the Republic of Turkey, as a country determined to embrace Western values and civilization and aspiring to promote intercivilizational dialogue at the UN level. Turning the Hagia Sophia Museum from a symbol of religious toleration and coexistence to a new symbolic battleground of a latter-day “clash of civilizations” is an ominous development with long-term domestic and international repercussions.