Why do some societies embrace religious diversity while others struggle with exclusion? Faith and Friendship reveals how the friendships we form-and those we avoid-shape interfaith attitudes across the Muslim world. Drawing on large-scale surveys from Indonesia and beyond, the book shows that religiously homogeneous friendships can unintentionally nurture stereotypes and social divides. Introducing the Boundaries, Opportunities, and Willingness (BOW) Framework, the book explains how state policies, civic spaces, and personal choices combine to determine whether people connect across faith lines. Blending rigorous research with vivid human stories, Faith and Friendship offers a new way to understand the roles of religion and social networks in everyday life and provides insights for anyone seeking to bridge interfaith divides.