 Henry lists a number of different skeptical arguments, drawing from the critical accounts of Aristotle, Cicero, Augustine, and Averroes, and mentioning the support skepticism garners from the views of Heraclitus, Zeno, Protagoras, and Democritus, and Plato. He gives no evidence here of having direct access to any of the texts of the latter five thinkers, though he knows of their views through the works of others.