Book excerpt: Freedom of religion is a subject, which has throughout human history been a source of profound disagreements and conflict. In the modern era, religious-based intolerance continues to provide lacerative and tormenting concern to the possibility of congenial human relationships. As the present study examines, religions have been relied upon to perpetuate discrimination and inequalities, and to victimise minorities to the point of forcible assimilation and genocide. The study provides an overview of the complexities inherent in the freedom of religion within international law and an analysis of the cultural-religious relativist debate in contemporary human rights law. As many of the chapters examine, Islamic State practices have been a major source of concern. In the backdrop of the events of 11 September 2001, a considerable focus of this volume is upon the Muslim world, either through the emergent State practices and existing constitutional structures within Muslim majority States or through Islamic diasporic communities resident in Europe and North-America.