The Copernican Method Against the Copernican Principle: Anthropic Typicality over Partial Information States

Given one natural-historical result carried in a companion development, three commitments, each independently plausible, cannot all be true: that one’s own situation is typical among observer-situations; that typicality is assessed under the cosmic weighting over possible histories rather than a gerrymandered alternative; and the astrobiological Copernican principle, on which observer-bearing environments like Earth’s are common. This paper derives the conditional inconsistency from a single principle—the Accordance Principle—governing typicality over partial, observer-indexed information states rather than complete histories, and then prices the three exits. The principle itself is one application of Bayes’ theorem away from the two mediocrity commitments; its application to the natural-historical record — carried in a companion development and imported here as a stated premise rather than re-argued — establishes the Rare Earth hypothesis; and Rare Earth contradicts the Copernican principle directly. The recommended exit is the third, and the reason is structural rather than empirical taste: the generalization of the very method that has always supported the Copernican principle—Copernican typicality reasoning itself—is what produces the constraint that overturns it. The framework differs from observation-selection theory by two relocations: the reference class ranges over observer-situations across possible histories, and the object of reasoning is a partial state rather than a completed timeline. On this diagnosis the tradition’s reference-class problem is an artifact of the completion. The natural-historical program built on the principle—its conjectures, its quantitative bounds, its predictions—is deliberately fenced to the companion.