Natural law is a concept that suggests a code, law, or set of rights inherent to existence and quite distinct from human created legal systems. Though difficult to codify, ideas of natural law, such as freedom and the right to pursue happiness, have greatly influenced nearly every legal system in the world. The theory also suggests that certain concepts are universal and should apply everywhere. This is opposed to human law, also called positive law, which may only extend as far as a jurisdiction allows.
The concept has existed since the dawn of written philosophy; Aristotle is typically considered the father of the idea, but his theories were greatly expanded on by later philosophers such as Thomas Aquinas. Many religious sects also include natural law as part of a belief system or code of ethics, but typically distinguished it from positive law or rules of behavior handed down by a divine figure, such as the Ten Commandments. In most religious philosophy, natural laws can always be supplanted by divine laws.
Several philosophical documents have attempted to list the premises of natural law, but the concept is somewhat difficult to establish. Since the theory is dependent on beliefs and individual ethical codes, there are nearly always contradictory ideas. Moreover, the basic theory of natural law suggests that it is separate from positive law, and therefore some argue it is not meant to be codified specifically. Often, the basic premise of this theory is reduced to a simple concept: people should strive to be good, and avoid being evil. Every idea past this point, including the definitions of “good” and “evil,” is highly debated.
Unlike positive law, which regulates actions, natural law tends to guide concepts of morality. For instance, murder may be considered illegal by positive law, but the idea that murder is morally wrong is a natural law theory. In addition to guiding ethics, Aristotle, Thomas Aquinas and many other philosophers suggest that natural laws are built into the fabric of the universe, and thus guide human concepts of reason and rationality.
Although natural laws in themselves are difficult to nail down, the influence of the concept exists throughout society. Protection of the innocent, the right to free expression, property rights, charitable acts, and the right to marriage are all related to legislative concepts of natural law. Belief in natural laws is the backbone behind societal ideas of justice; if a law is called unjust, it is because it is found to be morally, rather than legally, reprehensible. Whether or not the universe is actually built with natural ideas of rights and ethics embedded in existence, the belief that this type of law exists prevents positive law from being arbitrary and allows for concepts such as justice and basic rights to influence the creation of legal systems.