At the epistemic core lies a paradox of testimony and selfhood. If observers inhabit a spectrum of near-identical but diverging histories, then knowledge claims acquire a contextual index that is both local and trans-branch. I develop a formal apparatus for indexical credences that preserves rational coherence while accommodating cross-world divergence, showing how agents can update credences when confronted with evidence that is probabilistically informative across multiple branches. The result is an ethics of belief that ties responsibility to the recognition of alternative outcomes: to know is to acknowledge the moral weight of paths not taken.

Finally, the multiverse reframes political and aesthetic imagination alike. Institutions and narratives that assume a single, determinate past must be rethought as contingent constructions whose legitimacy depends on their resilience across possible histories. By foregrounding resilience and plural accountability, the thesis proposes practical criteria for policy and art that are robust under modal variation. In doing so, it offers a new vocabulary for thinking about contingency, responsibility, and creativity in a world where possibility is not an abstract margin but the very fabric of reality.