Perhaps no Greek philosopher expressed this thought more succinctly than the pre-Socratic Xenophanes of Colophon, who wrote in fragment 34.4 of his great elegiac poem:
δόκος δ' ἐπὶ πᾶσι τέτυκται ( ΔΟΚΟΣ ΔΕ ΕΠΙ ΠΑΣΙ ΤΕΤΥΚΤΑΙ )
— literally, "Perception is wrought upon all things;" that is, "All things are a matter of perception."