The Coherent Arc Model of Purpose

Two people facing the same terminal diagnosis respond differently. One finds the prospect of death tolerable, even reconcilable with how they understand their life. The other is destabilised in a way that has little to do with the physical prognosis and everything to do with the condition of their self-model at the moment the diagnosis arrives. Standard accounts of existential distress, whether anchored in mortality salience, negative affect, or philosophical nihilism, cannot explain this difference without appealing to something more architecturally specific. The Coherent Arc Model provides that specification. Purpose, on this account, is the regulation of an abstract, evaluative, temporally extended self-identity toward coherent completion within constraint. It is a structural feature of high-functioning human cognition, one that emerges as the temporal self-horizon expands sufficiently to expose the possibility of arc foreclosure. Existential distress arises from the appraisal that an identity arc will fragment or be interrupted before it reaches a form of coherent expression. Where the arc is experienced as integrated and viable, termination at the boundary of the operative horizon, including death, need not produce destabilisation. The model specifies three structural layers of continuity, distinguishing the biological maintenance that all living systems require, the experiential regulation characteristic of conscious animals, and the identity-level regulation that is distinctively human in its full form. It traces how the temporal horizon expands across development, what calibration failures look like in clinical and ordinary life, and why identity coherence can, under specific conditions, outrank biological survival as a regulatory priority. These are structural predictions of the model, and they distinguish it from accounts that treat purpose as a psychological add-on to more fundamental biological or cognitive processes.