The concept of natural law was first developed in the Greek world and has been carried through to the present day. There are a number of different approaches to this concept. The Graeco-Roman tradition held that there was a natural law that was accessible to mankind through reason. Christian theorists adopted aspects of Cicero's Stoic philosophy, an example of natural law, because of its emphasis on moral content. The Christian legal philosophy that developed was in many ways a fusion between the fundamental Christian teachings and the adapted teachings of the Stoics (Kelly 102). Most recently, the idea of natural law stands in opposition to the positivist school. Natural law requires a minimal moral content as a prerequisite for viewing something as in contravention of the law, while the positivist school holds that the law is whatever the state (in whatever form that exists) says it is. The concept of the natural law has the advantage of being based on something immutable, though admittedly morality may differ somewhat from one society to another. Yet the fact that Christian doctrine and Stoic doctrine can unify around certain legal issues demonstrates how moral dictates can be transcendent and can serve as guides that stand more readily than do the temporary whims of individual rulers or states.
In the medieval world, natural law is represented by Thomas Aquinas, while the opposing force is ably recounted by Machiavelli. Machiavelli in The Prince seems to suggest that vice may sometimes replace virtue if the ends can be said to justify the means. This applies to the Prince because for Machiavelli, human nature tends toward evil and needs to be controlled. The ruler is thus given the right to use immoral means to consolidate and preserve the power that is necessary to keep society from disintegrating. The protection of the state is of paramount importance, and the Prince is justified to use whatever means are necessary...