What were the tropes used by Pyrrhonian skeptics?

Pyrrhonian skeptics utilized tropes—argumentative strategies designed to oppose knowledge claims—to induce epochē, or the suspension of judgment. By demonstrating that for every proposition there exists an equally compelling contradictory one, they aimed to lead individuals toward ataraxia (unperturbability).12

The most prominent sets of these tropes include:

• The 10 Tropes of Aenesidemus: These arguments highlight the difficulties in establishing the truth of sense perceptions due to the variability of human and animal observers, the nature of the objects perceived, and the complex relationship between the two.13
• The 5 Tropes of Agrippa: These focus on the "problem of the criterion," arguing that any attempt to justify a knowledge claim inevitably fails. They include:42
  1. Clash of opinions: Disagreements exist in both daily life and philosophical debate.4
  2. Infinite regress: Any proof requires a further proof, leading to an endless chain.4
  3. Relativity: Perceptions and judgments are relative to the subject and concomitant factors.4
  4. Hypothesis: Dogmatists merely offer unproven assumptions to avoid regression.4
  5. Circular reasoning: Philosophers attempt to prove the sensible by the intelligible and vice versa.4

Through these methods, Pyrrhonists sought to undermine dogmatic claims without asserting that knowledge is impossible.12