This critical volume focuses on the concept of deification in Christian intellectual history. It draws together Eastern Orthodox, Roman Catholic, and Protestant scholars to introduce and explain the theory of deification as a biblically rooted, central theme in the Christian doctrine of salvation in diverse eras and traditions. The book addresses the origin, development, and function of deification from its precursors in ancient Greek philosophy to its nuanced use in contemporary theological thought. The revival of interest in deification, which has often been seen as heresy in the Protestant West, heralds a return to foundational understandings of salvation in the Christian church before divisions of East and West, Catholic and Protestant.