Diogenes Laertius, Lives of Eminent Philosophers, BOOK I, Prologue
In the Italian school the order of succession is as follows: first Pherecydes, next Pythagoras, next his son Telauges, then Xenophanes, Parmenides,11 Zeno of Elea, Leucippus, Democritus, who had many pupils, in particular Nausiphanes [and Naucydes], who were teachers of Epicurus.
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ethics, as we have said, started with Socrates; while dialectic goes as far back as Zeno of Elea. In ethics there have been ten schools: the Academic, the Cyrenaic, the Elian, the Megarian, the Cynic, the Eretrian, the Dialectic, the Peripatetic, the Stoic, and the Epicurean.
Diogenes Laertius, Lives of Eminent Philosophers, BOOK IX, Chapter 5. ZENO OF ELEA
Aristotle says that Zeno was the inventor of dialectic, as Empedocles was of rhetoric