Full Idea
The Stoics are the originators of one of the most influential concepts in political philosophy, that of natural law. …It is simply correct moral reasoning, thought of as being prescriptive.
Gist of Idea
Stoics originated the concept of natural law, as agreed correct reasoning
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Julia Annas - The Morality of Happiness 13.3
Book Reference
Annas,Julia: 'The Morality of Happiness' [OUP 1995], p.302