"Who is Hindu, who is Muslim?" The answer, according to Dominique-Sila Kahn, is not as simple as is generally assumed. By analysing documentary sources as well as original field data, she examines the shaping of religious identities in South Asia, more particularly in North India. The author argues that the perception of Islam and Hinduism as two monolithic and perpetually antagonistic faiths co-existing uneasily in South Asia has become so deeply ingrained that the complexity of the historical fabric is often overlooked or ignored. She demonstrates how the emergence of clear-cut categories is a comparatively recent phenomenon, and shows how the past is characterized by a remarkable fluidity and diversity in the social and religious milieus of the two faiths. In exploring the historical mechanisms that have led to the emergence and crystallization of religious identities, the author sheds light on an increasing number of conflicts which threaten the harmonious co-existence of South Asian communities today.