Book I. The Philosophers

These are the contents of the First Part of the Refutation of all Heresies;

What were the tenets of the natural philosophers and who these were; and what those of the ethicists and who these were; and what those of the dialecticians and who the dialecticians were.

Now the natural philosophers mentioned are Thales, Pythagoras, Empedocles, Heraclitus, Anaximander, Anaximenes, Anaxagoras, Archelaus, Parmenides, Leucippus, Democritus, Xenophanes, Ecphantus, and Hippo. The ethicists are Socrates, pupil of Archelaus the physicist and Plato, pupil of Socrates. These mingled together the three kinds of philosophy. The dialecticians are Aristotle, pupil of Plato and the founder of dialectics, and the Stoics Chrysippus and Zeno.

Epicurus, however, maintained an opinion almost exactly contrary to all these. So did Pyrrho the Academic who asserts the incomprehensibility of all things. There are also the Brachmans among the Indians, the Druids among the Celts, and Hesiod.