In epistemology, rationalism is the view that "regards reason as
the chief source and test of knowledge" or "any view appealing
to reason as a source of knowledge or justification." More
formally, rationalism is defined as a methodology or a theory
"in which the criterion of the truth is not sensory but
intellectual and deductive." Rationalists believe reality has an
intrinsically logical structure. Because of this, rationalists
argue that certain truths exist that the intellect can directly
grasp. That is to say, rationalists assert that certain rational
principles exist in logic, mathematics, ethics, and metaphysics
that are so fundamentally true that denying them causes one to
fall into contradiction. Rationalists have such a high
confidence in reason that proof and physical evidence are
unnecessary to ascertain truth – in other words, "there are
significant ways in which our concepts and knowledge are gained
independently of sense experience." Because of this belief,
empiricism is one of rationalisms grea