This paper evaluates numerous positive and normative theories of justice in positive terms, i.e., in terms of how accurately they describe the impartial fairness preferences of real people. In addition, the paper proposes and defends an integrated justice theory based on preferences over four distinct and sometimes conflicting forces. These forces frame the analysis of the individual theories and inspire four corresponding theoretical classes: equality and need, utilitarianism and welfare economics, equity and desert, and context. This synthesis enables one to treat justice rigorously and to reconcile results that often appear contradictory or at odds with alternative theories.