Thomas Aquinas viewed human reason as a force parallel to divine guidance. Internally, he taught, we are guided by justice. Justice, in its most general sense, is a virtue that perfects the human will, causing us to do what is good and thereby contribute to proper interaction in society. Law, writes Aquinas, is an external expression of justice. At its simplest, law is the societal rule that guides us toward good. Reason, then, which is the foundation of law, is a path to good. -- Classics of Liberty ( )