/ Dictionary / Index P pure reason: Meaning and Definition of Find definitions for: pure' rea'son Pronunciation: [key] — Kantianism. Kantianism. reason based on a priori principles and providing a unifying ground for the perception of the phenomenal world. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. purely purfle Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language