Extract the answer to the question from the following context. Question: What defining institution of the Greek world was rejected by those who promoted atomism an an asceticism based on freedom from pain, as well as by those who rejected all material possessions and social conventions? Context: The Epicureans and the Cynics rejected public offices and civic service, which amounted to a rejection of the polis itself, the defining institution of the Greek world. Epicurus promoted atomism and an asceticism based on freedom from pain as its ultimate goal. Cynics such as Diogenes of Sinope rejected all material possessions and social conventions (nomos) as unnatural and useless. The Cyrenaics meanwhile, embraced hedonism, arguing that pleasure was the only true good. Stoicism, founded by Zeno of Citium, taught that virtue was sufficient for eudaimonia as it would allow one to live in accordance with Nature or Logos. Zeno became extremely popular, the Athenians set up a gold statue of him and Antigonus II Gonatas invited him to the Macedonian court. The philosophical schools of Aristotle (the Peripatetics of the Lyceum) and Plato (Platonism at the Academy) also remained influential. The academy would eventually turn to Academic Skepticism under Arcesilaus until it was rejected by Antiochus of Ascalon (c. 90 BCE) in favor of Neoplatonism. Hellenistic philosophy, had a significant influence on the Greek ruling elite. Examples include Athenian statesman Demetrius of Phaleron, who had studied in the lyceum; the Spartan king Cleomenes III who was a student of the Stoic Sphairos of Borysthenes and Antigonus II who was also a well known Stoic. This can also be said of the Roman upper classes, were Stoicism was dominant, as seen in the Meditations of the Roman emperor Marcus Aurelius and the works of Cicero.
Answer:
the polis