Despite its polemical anti-authoritarian stance on religion, Philip Pullman’s children’s fantasy trilogy, His Dark Materials, edifies the ideological separation of adult and child. The primacy of so-called adult characteristics reflects the influence of authoritarian ideologies on Pullman’s writing. In the study below, with a special focus on the essentializing developmental framework Pullman deploys to structure Lyra’s growth from childhood to young adulthood, I show how the HDM trilogy replicates many of the frameworks it disavows. Building on existing scholarship, I present the broader influence of Christian values on Pullman’s trilogy despite his antagonism towards Christianity’s impact on children’s literature. Additionally, while acknowledging Pullman’s rebellion against the frequently religious generic conventions of children’s literature established by J.R.R. Tolkien and C.S. Lewis, I expand on this connection to argue that Pullman’s disdain for fantasy is connected more broadly to the history of children’s literature and colonialism, and that this interplay highlights the ongoing connection between empire and the English canon which complicates Pullman’s anti-authoritarian and anti-theistic quest for a republic of heaven in the His Dark Materials Trilogy. By connecting Lyra’s developmental trajectory to the influence of Christianity and imperialism within the institutional norms of education, children’s literature, and psycho-medical discourses, I ultimately argue that we should be skeptical of the developmental model HDM proposes, and the values it upholds.