Ra"tion*al*ism (răsh"ŭn*al*&ibreve;z'm), n. [Cf. F. rationalisme.] 1. (Theol.) The doctrine or system of those who deduce their religious opinions from reason or the understanding, as distinct from, or opposed to, revelation.

2. (Philos.) The system that makes rational power the ultimate test of truth; -- opposed to sensualism, or sensationalism, and empiricism. Fleming.