Idealism

The term idealism in its broadest sense denotes the philosophical position that ideas (mental or spiritual entities) are primary and lie at the very foundation of reality, knowledge, and morality, while non-ideal entities (such as physical or material things) are secondary and perhaps even illusory. Strands of idealistic thought can be found in ancient and medieval philosophy, but modern idealism begins in the wake of René Descartes (1596–1650), whose method of doubt problematized the relation of the mind (or spirit or ideas) to the material world and thus raised questions about how ideas "inside" the mind can be known to interact with or correspond to any material, extended thing "outside" the mind.