One of the significant contributions of contemporary American legal realism has been the discussion of the origins, purpose, and efficacy of legal rules. Some writers have been extremely critical of the worship of legal rules and of the feeling by the lay public that rules can provide exactness and certainty in the law. Jerome Frank has been the most noteworthy exponent of this view, particularly in his pioneer book, Law and the Modern Mind, published in 1930.

Frank would be the last person to deny the existence and the utility of legal rules. Yet, his attack on those writers who see only the legal rules and nothing else as law (especially the late Professor Joseph Beale) has led some writers to believe that Frank wanted a legal system that operated on a purely pragmatic basis. Frank fervently denies this accusation and says that men like Gray, Wigmore, and Judge Cuthbert Pound expressed similar doubts about the prediction value of legal rules and precedents.