Pronunciation: (rash'u-nl-iz"um),[key] —n. 1. the principle or habit of accepting reason as the supreme authority in matters of opinion, belief, or conduct.
2. Philos. a. the doctrine that reason alone is a source of knowledge and is independent of experience.
b. (in the philosophies of Descartes, Spinoza, etc.) the doctrine that all knowledge is expressible in self-evident propositions or their consequences.
3. Theol.the doctrine that human reason, unaided by divine revelation, is an adequate or the sole guide to all attainable religious truth.
4. Archit.(often cap.) a. a design movement principally of the mid-19th century that emphasized the development of modern ornament integrated with structure and the decorative use of materials and textures rather than as added adornment.
b. the doctrines and practices of this movement. Cf. functionalism (def. 1).