natural law

noun

1. a principle or body of laws considered as derived from nature, right reason, or religion and as ethically binding in human society.

noun

1. an ethical belief or system of beliefs supposed to be inherent in human nature and discoverable by reason rather than revelation
2. a nonlogically necessary truth; law of natureSee also nomological (def. 2)
3. the philosophical doctrine that the authority of the legal system or of certain laws derives from their justifiability by reason, and indeed that a legal system which cannot be so justified has no authority

The doctrine that human affairs should be governed by ethical principles that are part of the very nature of things and that can be understood by reason. The first two paragraphs of the Declaration of Independence contain a clear statement of the doctrine.