Multiple rationalities

Chapter 8 argues for permissive rationality: probabilism is the only internal rational requirement, making any probability function rationally permissible from the agent's own perspective. However, the chapter introduces ecological rationality to evaluate doxastic states by their success in specific environments rather than abstract possibility spaces. Using examples like the Müller-Lyer illusion and cross-cultural perception studies, Easwaran shows how systems can be ecologically adapted yet fail in unusual circumstances. Philosophical case studies (fake barns, evil demon, clairvoyance) are reanalyzed through this ecological lens. The chapter distinguishes ideal from non-ideal rationality, arguing that non-ideal agents shouldn't necessarily aim toward theoretical ideals but toward practical success in their actual environments. An evolutionary analysis suggests cognitive dispositions shaped by natural selection may serve reproductive fitness rather than truth or preference satisfaction, potentially creating systematic biases while remaining ecologically successful in ancestral environments.