Concept brief introducing Predictive Developmental Psychology (PDP), a developmental account of trauma centred on uncertainty regulation. The brief argues that early holding keeps uncertainty within a tolerable learning range, allowing prediction error to support learning rather than signal threat to psychological continuity. It outlines the core mechanism, the affective sequence from dread to despair, the emergence of ultimate strategies, and the concept of expected viable states. A fuller monograph and companion notes, including an active-inference framing, are available on request.