This paper provides a relational analysis of James Fowler's Faith Development Theory and Heinz Streib's Religious Styles Perspective in light of a recent study of apostasy from religious fundamentalisms. Empirical support is provided for both theories. RSP is endorsed as a more encompassing theory of religious development which accounts for more contingencies than FDT. However, FDT is subsumed rather than superseded by RSP as a powerful lens through which to observe cognitive dimensions of religious development. The paper introduces an integrative (...) paradigm, phenomenological empiricism, to conceptualise a complementary relationship between FDT and RSP as key theories in the future study of religious development. (shrink)