 PH 1, which figures most prominently in scholarly discussions, is a tour de force. Sextus gives a general account of what skepticism is, including skeptical investigation, suspension of judgment, the skeptic’s end, action, and language; he gives lists and illustrations of various sets of Modes; he explains the so-called skeptical formulae (phônai), such as “I determine nothing,” “non-assertion,” “maybe,” and so on; and he compares skepticism to relevantly similar philosophies.