Explain the Greek conception of nature (physis). ?

Philosophers commonly appeal (explicitly of implicitly) to nature in order to justify their arguments. Explain the Greek conception of nature (physis) (hint: teleology). Yet Plato and Aristotle bring different nuances to this general view: Plato has an a priori (or idealist) theory, Aristotle an empirical and ytic interpretation. How do these differences affect their arguments concerning the organization of society and the designation of roles to different people and cles in society? When Cicero claims that justice is “right reason applied to nature” does he maintain or modify the Greek conception of nature? (Hint: his rationalist vision of natural law and its relation to positive law are important here.)