The most important Muslim practices are the Five Pillars of Islam. The Five Pillars of Islam are the five obligations that every Muslim must satisfy in order to live a good and responsible life according to Islam.Shia and Sunni are the two branches of Islam. They share most of the basic tenets and principles of the religion. Differences between Shias and Sunnis initially stemmed from political strife and not any spiritual disagreements. These differences originally appeared after the passing away of Prophet Muhammad (PBUH). The so-called division of Muslims between Shia and Sunni is akin to the differences between Catholics and Protestants.It's not known precisely how many of the world's 1.3 billion Muslims are Shia. The Shia are a minority, comprising between 10 percent and 15 percent of the Muslim population — certainly fewer than 200 million, all told. The Shia are concentrated in Iran, southern Iraq and southern Lebanon. But there are significant Shiite communities in Saudi Arabia and Syria, Afghanistan, Pakistan and India as well. Although the origins of the Sunni-Shia split were violent, over the centuries Shia and Sunnis lived peacefully together for long periods of time. But that appears to be giving way to a new period of spreading conflict in the Middle East between Shia and Sunni.When Lesley Hazleton was writing a biography of Muhammad, she was struck by something: The night he received the revelation of the Koran, according to early accounts, his first reaction was doubt, awe, even fear. And yet this experience became the bedrock of his belief. Hazleton calls for a new appreciation of doubt and questioning as the foundation of faith — and an end to fundamentalism of all kinds.