skepsis

Greek skepsis (σκέψις) meant inquiry, examination, careful looking — from skeptesthai, to look carefully, to examine. The Skeptic philosophers (Pyrrhonists, named for Pyrrho of Elis, c. 360-270 BCE) argued that for every claim, equally strong arguments could be made for and against it. Since equally balanced arguments could not rationally produce certainty, the wise response was epoché — suspension of judgment. Neither affirm nor deny; observe the equipoise.

Pyrrho reportedly took his philosophy seriously enough that his friends had to prevent him walking in front of carts. If you genuinely suspend judgment about whether carts are dangerous, walking in front of them may follow. His student Timon of Phlius wrote: Pyrrho's teacher Anaxarchus, a philosopher of the same school, walked into a swamp when he saw that other philosophers avoided it — he refused to judge the swamp dangerous. Radical skepticism has practical consequences.

The Roman Academy under Carneades (214-129 BCE) developed Academic Skepticism — a less radical position. Rather than suspending all judgment, Academic Skeptics held that some beliefs were more probable than others and could be acted on, though none could be known with certainty. This 'probabilism' was more livable than Pyrrhon's suspension and influenced later thinkers from Cicero to John Locke.

Modern scientific skepticism is a positive program: claims should be proportionate to evidence; extraordinary claims require extraordinary evidence; established consensus should be updated when evidence demands. Carl Sagan's 'Baloney Detection Kit' and the Skeptical Inquirer magazine codified this as a popular practice. The careful looking of ancient Greeks became the methodology of evidence-based inquiry.