How, if at all, do Muslims and non-Muslims differ? The question spurs spirited discussion among people the world over, in Muslim and non-Muslim lands alike, but we still lack answers based on sound empirical evidence. This book engages a set of the biggest issues using rigorous methods and data drawn from around the globe. It reveals that in some areas Muslims and non-Muslims differ less than is commonly imagined. It shows that Muslims are not unusually religious or inclined to favor the fusion of religious and political authority. Nor are Muslims especially prone to mass political violence. Yet in some areas Muslims and non-Muslims diverge: Gender inequality is more severe among Muslims, Muslims are unusually intolerant of homosexuality and other controversial behaviors, and democracy is rare in the Muslim world. Other areas of divergence bear the marks of a Muslim advantage: Violent crime and class-based inequities are less severe among Muslims than non-Muslims. Committed to discovering social facts rather than either stoking prejudices or stroking political sensibilities, this book represents the first major scientific effort to assess how Muslims and non-Muslims differ-and do not differ-in the contemporary world. Its findings have vital implications for human welfare, interfaith understanding, and the foreign policies of the United States and other Western countries.