The Pyrrhonian Modes are argument schemata for general use against dogmatism. We have records of two main lists of Modes, the Ten and the Five, which were used at various times in the history of ancient scepticism, either independently or in some sort of systematic connection. These Modes use strategies with ancient roots in such thinkers as Protagoras, Democritus, Plato, and Aristotle, but users of the Modes were not committed to positions held by those thinkers. They were compiled long after Pyrrho (the Ten probably by Aenesidemus and the Five by a shadowy figure named Agrippa) during the first phase of the Pyrrhonian revival. In addition, we have a list of eight causal Modes attributed to Aenesidemus.

The second and final phase of Pyrrhonism occupies most of the works of Sextus Empiricus (apart from Against the Ethicists, M 11). Although he has different strategies from Aenesidemus, he lays out the Ten Modes in some detail and makes extensive use of the Five. His account of the Ten is sometimes at odds with his general practice, and this is most likely due to his use of sources from the first phase of the revival.

Besides Sextus (PH 1.36–163), we have two main sources for the Ten Modes: Diogenes Laertius (9.78–88) and Philo of Alexandria (On Drunkenness 169–202), both of whom seem to have a source independent of Sextus. Diogenes is just reporting what he knows, whereas Philo appropriates eight of the Modes for his own purpose and leaves out the other two (the Third and Ninth in the list according to Sextus). Brief mentions by Aristocles and Herrenius do not add to our understanding.