Because of the ambiguity of the word nature, the meaning of natural varies. Thus, natural law may be considered an ideal to which humanity aspires or a general fact, the way human beings usually act. Natural law is contrasted with positive law, the enactments of civil society. The ancient Greek philosophers were the first to elaborate a natural law doctrine. The Stoics, especially the philosopher Chrysippus of Soli, constructed a systematic natural law theory.
Every individual nature is part of the cosmos.
To live virtuously means to live in accord with one's nature, to live according to right reason. Because passion and emotion are considered irrational movements of the soul, the wise individual seeks to eradicate the passions and consciously embrace the rational life. There will not be different laws at Rome and at Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and for all times. Christian Conceptions Print section Christians found the natural law doctrine of the Stoics quite compatible with their beliefs. The teaching of St. Thomas Aquinas on the natural law is the most widely known.