Antiochus joined the Academy, the school founded by Plato, late in the second century BCE, when Philo of Larissa was its head. Philo was (at this time) a moderate Academic skeptic who had been convinced by the Academy's anti-Stoic arguments that nothing can be known for certain, but he did not embrace the other doctrine for which Academic skeptics argued—suspension of judgment. According to Philo, although certain knowledge is unobtainable, it is possible to identify highly probable impressions, and there is no reason not to accept them, provided that one realizes that one might be wrong. Prominent among them is the impression that nothing can be known.

After defending this view for many years, Antiochus became a dogmatist by accepting that knowledge is possible. His epistemological position was now essentially that of the Stoa. He responded to accusations that...