Pragmatism is a philosophical theory of knowledge whose criterion of truth is relative to events and not, as in traditional philosophy, absolute and independent of human experience. A theory is pragmatically true if it "works" – if it has an intended or predicted effect. All human undertakings are viewed as attempts to solve problems in the world of action; if theories are not trial solutions capable of being tested, they are pointless. The philosophy of pragmatism was developed in reaction to late 19th-century idealism mainly by the American philosophers Charles Peirce, John Dewey, and William James. See also instrumentalism.