In philosophy, natural law is a system of right or justice held to be common to all humans and derived from nature rather than from the rules of society, or positive law. There have been several disagreements over the meaning of natural law and its relation to positive law. Aristotle held that what was “just by nature” was not always the same as what was “just by law.” This also formulated the debate whether the Laws of man were compatible with the Laws of God.
Augustine, like Plato’s theory, suggested a clear contrast between the laws of humans and the laws of God. Later, taking these ideas a step further, St. Thomas Aquinas propounded an influential systematization, maintaining that, though the eternal law of divine reason is unknowable to us in its perfection as it exists in God’s mind, it is known to us in part not only by revelation but also by the operations of our reason. The law of nature, which is “nothing else than the participation of the eternal law in the rational creature,” thus comprises those precepts that humankind is able to formulate – namely, the preservation of one’s own good, the fulfillment of “those inclinations which nature has taught to all animals,” and the pursuit of the knowledge of God. Human law must be the particular application of natural law.
For example, an important part of Natural law is ‘Just War’. Although most religions including Christianity support pacifism, politics makes war necessary at times. Here, based on the ideas of Augustine again, Aquinas proposes that a just war is: rightful in intention, based on a just cause, and under the authority of the sovereign.
