Diogenes Laertius Vitae philosophorum 9.11.61

[61] Pyrrho of Elis was the son of Pleistarchus, as Diocles relates. According to Apollodorus in his Chronology, he was first a painter; then he studied under Stilpo’s son Bryson ¹ : thus Alexander in his Successions of Philosophers. Afterwards he joined Anaxarchus, whom he accompanied on his travels everywhere so that he even forgathered with the Indian Gymnosophists and with the Magi. This led him to adopt a most noble philosophy, to quote Ascanius of Abdera, taking the form of agnosticism and suspension of judgement. He denied that anything was honourable or dishonourable, just or unjust. ² And so, universally, he held that there is nothing really existent, but custom and convention govern human action; for no single thing is in itself any more this than that.