We apply the displacement framework to sleep and sleep disorders. The central claim is that sleep is biology's most universal mandatory return: wakefulness is a controlled, high-displacement condition in which metabolic, synaptic, and neural systems accumulate displacement _wake whose cost must be serviced nightly. We define the biological sleep ground state S^0_sleep, model wakefulness as controlled departure from it, and identify adenosine as the primary signal of accumulated displacement cost.
NREM sleep is formalized as deep ground-state restoration, and REM sleep as active emotional-displacement processing. Insomnia is analyzed as a wrong attractor in the return pathway — a stable high- configuration that prevents entry into the return path. Chronic sleep restriction is modeled as the accumulation of unresolved displacement = D()\,dt whose recovery cost exceeds prevention cost by DC5 (irreversibility).
Sleep medicine — CBT-I, pharmacology, stimulus control — is reinterpreted as return-pathway facilitation: interventions that lower the attractor basin of the wrong state or clear obstructions on the return path. The framework provides a unified quantitative language for phenomena previously described only empirically.
Phronesis