The Noonday argument: fine-graining, indexicals, and the nature of Copernican reasoning

Abstract Typicality arguments attempt to use the Copernican Principle draw conclusions about cosmos and presently unknown conscious beings within it, including extraterrestrial intelligences (ETI). The most notorious is Doomsday Argument, which purports constrain humanity's future from its current lifespan alone. These rest on a likelihood calculation that penalizes models in proportion number of distinguishable observers. I argue such reasoning leads solipsism, belief one only being world, therefore unacceptable. Using variants ‘Sleeping Beauty’ thought experiment as guide, present framework for evaluating observations large cosmos: Weighted Fine Graining (WFG). WFG requires construction specific physical outcomes observations. Valid typicality then emerge combinatorial properties third-person microhypotheses. Indexical (observer-relative) facts do not directly theories, but instead weight different provisional evaluations credence. As indexical knowledge changes, weights shift. show self-applied Argument fails WFG, even though it can work an external observer. does let us apply self-observations ETIs.