The American Realist movement developed during the 1930s from the philosophical views associated with James and Dewey. Both rejected ‘closed systems, pretended absolutes and origins’ and turned towards ‘facts, action and powers’. James insisted upon the study of ‘factual reality’; Dewey called for an investigation of probabilities in law and reminded jurists that ‘knowledge is successful practice’. The realists studied law on the basis of a rejection of ‘myths and preconceived notions’ and on the acceptance of recording accurately things as they are as contrasted with things as they ought to be. A true science of law demands a study of law in action. ‘Law is as law does.’ The three jurists noted in this chapter, who contributed to the foundations and growth of American Realism, are Holmes (1841-1935), Gray (1839-1915) and Cardozo (1870-1938).