noun

• (philosophy) The theory that the reason is a source of knowledge independent of and superior to sense perception.
• (philosophy) The theory that knowledge may be derived by deductions from a priori concepts (such as axioms, postulates or earlier deductions).
• A view that the fundamental method for problem solving is through reason and experience rather than faith, inspiration, revelation, intuition or authority.
• Elaboration of theories by use of reason alone without appeal to experience, such as in mathematical systems.