The Organization of Islamic Cooperation (OIC), founded in 1969, is the largest intergovernmental organization after the U.N. It is the largest platform of Muslim countries that cover a range of political, economic and cultural issues. Its 13th Leaders Summit where Turkey took over the presidency for the next two years was held in Istanbul on April 14-15 with the agenda of "Unity and Solidarity for Justice and Peace." The title says much about the current challenges the Muslim world faces today. It also hints at the opportunities that member states have before them.The summit agenda was focused on one simple but key idea: There will not be peace and justice without unity and solidarity among nations. To overcome their current malaise and realize their true potential, Muslim nations have to create an agenda of common interest that will serve individual countries as well as the group as a whole. This is easier said than done. It is a challenge to create a situation where group interest serves everyone and the concerns and priorities of individual members are addressed in a way that empowers both the group and its members.The problem with the OIC is the same that all international organizations such as the U.N. and EU face: Each member wishes to see the group as a platform to prioritize its own issues and concerns. True, there are issues of plain common interest such as Palestine, for which the OIC was initially established, Muslim minorities, inter-member trade, or Islamophobia. But even then there are differences as to how to define and resolve them. It is natural for member states to lobby for their own issues. The key here is to find ways to maximize the interests of individual members while strengthening group solidarity that will in turn help individual countries. It is here that unity and solidarity assume supreme importance.Peace and justice are key issues not only for the current Muslim world but also an essential part of the Islamic faith and tradition. Two of God's beautiful names are "peaceful" (as-salam) and "just" (al-adil). The word "Islam" comes from the same root, i.e., silm, and means peace. It is such a great irony that the religion whose root meaning is peace has come to be associated with violence and terrorism in the modern world. Furthermore, those who blow themselves up in the name of religion claim to justify their acts of violence and terrorism on the grounds that they are fighting for justice. No two concepts have been as twisted and tortured as peace and justice.Grounded in the divine reality, peace and justice form the foundation of the cosmic and human orders. As a matter of fact, there is no peace without justice. No peace will be genuine and sustainable without a just and fair foundation. Most peace initiatives fail because they lack the core element of justice and fairness. Palestine and the Middle East peace process is a case in point. The same applies to many other conflicts around the world.We need to define unity and solidarity in a proper manner. Unity does not mean uniformity. It does not suggest a banal sameness on all issues. To the contrary, unity already implies an element of difference. The concept of unity-in-diversity, which the classical Muslim scholars have developed over the centuries, refers to this essential truth whereby we deepen our unity while maintaining our unique differences that enrich us as individuals and as a group.The long list of issues addressed at the 13th OIC Summit in Istanbul already presents an ambitious agenda. But each issue, while important in its own right, will have meaning and resolution only when it is addressed with an understanding of unity-in-diversity.The scourge of terrorism led by DAESH, al-Qaida, Boko Haram, al-Shabab, the PKK and others targets Muslims more than others and requires Muslim countries to have better cooperation and intelligence-sharing among themselves. But killing terrorists is not enough. Muslim religious and political leaders have to do more to stop the wave of radicalization that feeds violent extremism. They have to win the hearts and minds of young people before they lose their anchor in the truth.Sectarianism is another urgent issue that is fueling division, generating hatred and undermining unity and justice in the Muslim world. The current tensions between Sunni and Shiite Muslims are not so much about religion or sect per se as they are about nation-state rivalries and power struggles that engulf ordinary Muslims in an endless cycle of blame, defamation and guilt-by-association. From Iran, Iraq and Lebanon to Saudi Arabia, Kuwait and Pakistan, all Muslim countries have to find ways to overcome the current impasse and realize that before being Sunni or Shiite we are all Muslims, believe in the same Quran, follow the same prophet and face the same qibla.The OIC summit in Istanbul discussed such pressing issues as failed states and weak governments, poverty, youth unemployment, environmental hazards, bad urban development, lack of equal opportunity, violence against women, education, humanitarian aid and micro-financing. These are critical issues and there is no magical formula to solve them overnight. But a strong commitment to unity and solidarity without necessarily having to agree on everything can go a long way to open up new opportunities for the Muslim world. Realizing peace and justice first in our souls and then in our communities, nations and regions can help us overcome many of the problems we are facing today.