A collection of essays argues that evolutionary and experimental methods demand a revision of traditional philosophical concepts. The author examines how notions of knowledge, truth, and consciousness must be reframed through an empirical, pragmatic lens. He critiques intellectualist and idealist doctrines, defends immediate empiricism, and outlines an experimental approach to intelligence and morals. Several pieces consider the social and ethical consequences of adopting a naturalistic, historicized view of beliefs and urge tentative, piecemeal reconstruction of philosophical doctrines.