Its derivation is from justitia . For, in terms of Celsus' elegant definition, the law is the art of goodness and fairness. Practical wisdom in matters of right is an awareness of God's and men's affairs, knowledge of justice and injustice. From the precepts of the natural law, as from common and indemonstrable principles, the human reason needs to proceed to the more particular determination of certain matters. These particular determinations are called human laws, provided that the other essential conditions of law be observed.
Every human law has just so much of the nature of law as it is derived from the law of nature.
But if in any point it departs from the law of nature, it is no longer a law but a perversion of law. . . . Some things are . . . I comply not with your wish, the expression or intimation of your wish is a command . But where it obliges to a specific act or forbearance, or to acts or forbearances which it determines specifically or individually, a command is occasional or particular. In all or most cases of human superiority, the relation of superior and inferior, and the relation of inferior and superior, are reciprocal.