This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book seeks to contribute to the rethinking of the nature of Indonesian Islam that these comments suggest and, in particular, the approach of Indonesia's post-Soeharto religious and political leaders towards religious minorities, both Muslim and non-Muslim. It deals more specifically with 'Freedom of Religion under the Constitution'. In it, Simon Butt examines the nature of freedom of religion in the Constitution and tracks cases examined by the Constitutional Court, including the Religious Courts case, the Polygamy case and the Blasphemy Law case. Melissa Crouch investigates the role of the state in promoting and maintaining equality between religious communities and Greg Fealy introduces Part II with an essay that sets a framework for political analysis of religious intolerance in Indonesia. Arskal Salim looks at how the enactment of Perda Syariah across Indonesia at the local level has enabled discrimination against vulnerable groups.