2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/186072Perturbative gravity about a de Sitter background motivates a global picture of quantum dynamics in `eternal de Sitter space,' the theory of states which are asymptotically de Sitter to both future and past. Eternal de Sitter physics is described by a finite dimensional Hilbert space in which each state is precisely invariant under the full de Sitter group. This resolves a previously-noted tension between de Sitter symmetry and finite entropy. Observables, implications for Boltzmann brains, and Poincare recurrences are briefly discussed.17 pages, 1 figure. v2: minor changes, references added. v3: minor changes to correspond to PRD versionHigh Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext