Ethics

Epicurean ethics is fundamentally revisionary.

Instead of taking current popular views as basically valid (e.g. as Aristotle readily espoused those of the free-born, all-male, landed/wealthy, Athenian aristocracy), and deducting generally applicable principles from them, Epicurus viewed the "beliefs of the many" as basically flawed: humanity was (and, Epicurus would certainly argue, still is) seriously ill, stricken with the disease of anxiety; it therefore needs help, in order to gain or regain health, which he understood as the lack of that very same anxiety; and the only cure for human malaise was philosophy, specifically that sort of philosophy that led the way to ataraxia, the absence of anxiety.

And that particular brand of philosophy, of course, was the one Epicurus propagated, taught, or "preached".