The Quest for Certainty, considered against the background of traditional philosophies, is a revolutionary work. John Dewey does not claim that all the ideas in his book are original, but he justifiably asserts that if the ideas outlined in his book were implemented, a revolution comparable to the Copernican would be effected not only in philosophy but also in the moral, social, and economic dimensions of daily life. That this claim is a valid one is partially verified by the pervasive influence of Dewey’s teachings on many phases of American culture, especially on education. That Dewey’s works should have such an influence is especially appropriate in view of his constantly recurring emphasis on the importance of an intimate, reciprocal relationship between theory and practice. Regardless of whether one finds all of Dewey’s methods and conclusions acceptable, it is undeniable that the author’s searching criticism of older theories combined with constructive suggestions of remedial and progressive measures have profound practical import.