"The truth is hypothetical."
Scepticism (or skepticism), the belief that requires all information to be well supported by evidence, originated in the Skeptikoi, a first century BC Greek school who "asserted nothing." The school was founded by Aenesidemus; our main source of the school's teachings is Sextus Empiricus and the leader of the Sceptics was Pyrrho of Elis (365-275 BC) who had traveled to India and studied with the gymnosophists ('naked lovers of wisdom'). From India, Pyrrho brought back the idea that nothing can be known for certain. The senses are easily fooled, and reason follows too easily our desires. Along with Stoicism and Epicureanism, Scepticism was one of the three dominant schools of Hellenistic Philosophy.
A sextet of sceptic texts has been collected in this anthology:
Pyrrhonic Sketches by Sextus Empiricus.
Life of Pyrrho by Diogenes Laërtius.
Sextus Empiricus and Greek Scepticism by Mary Mills Patrick.
The Greek Sceptics: from Pyrrho to Sextus by Norman MacColl.
Stoics and Sceptics by Edwyn Bevan.
Life of Carneades by Diogenes Laërtius.
A key concept for the sceptics was ataraxia ("tranquility"), a Greek term used by Pyrrho to describe a lucid state of robust tranquility, characterized by ongoing freedom from distress and worry. By applying ideas of what he called "practical skepticism" to Ethics and to life in general, Pyrrho concluded that ataraxia could be achieved. Arriving at a state of ataraxia became the ultimate goal of the early Skeptikoi.
"Skepticism is the first step toward truth."
- Denis Diderot
About the Author: Pyrrho of Elis (365-275 BC) is usually credited with initiating skepticism. Today Pyrrho's ideas are known mainly through the book Outlines of Pyrrhonism written by the Greek physician Sextus Empiricus.
Mary Mills Patrick (1850-1940) was a college president and author. She was a member of the psychological congresses at Munich in 1896 and at Paris in 1900; and of the philosophical congresses at Paris, 1900, and at Bologne in 1911.
Norman Maccoll (1843-1904) was for many years the editor of the Athenaeum.
Edwyn Robert Bevan (1870-1943) was a versatile English philosopher and historian of the Hellenistic world. He had an academic position at King's College London. Bevan was awarded an honorary doctorate from St. Andrews in 1922 and an honorary D.Litt. from Oxford in 1923. In 1942 he became a Fellow of the British Academy.
Diogenes Laertius (fl. c. 3rd century CE) was a biographer of the Greek philosophers. Nothing is known about his life, but his surviving Lives and Opinions of Eminent Philosophers is a principal source for the history of Greek philosophy.
Sextus Empiricus (c. AD 200), the main authority for Greek skepticism, developed the philosophy further, incorporating aspects of empiricism into the basis for asserting knowledge.