As Christians seek to follow Paul's example of becoming like all people in order to win them to Christ, a key question arises: How far is too far? Is there a point where appropriate contextualization becomes gospel-distorting syncretism? With the growing prominence of Insider Movements in the Muslim-majority world in recent decades, these questions have become especially urgent and hotly-debated. Based on an in-depth, biblical-theological study of key Bible texts used by Insider Movement proponents and critics, this book provides a ground-breaking new assessment tool for distinguishing contextualization from syncretism. It provides an invaluable resource for those engaged in ministry amongst Muslims, for those with questions about Insider Movement practices, and for all who seek to grow in their understanding and practice of biblically-grounded and authentic contextualization of the gospel.