Part of an inscription on an altar seen by the apostle Paul while at Athens. The Athenians expressed their fear of deities by building many temples and altars. They even went so far as to deify the abstract, erecting altars to Fame, Modesty, Energy, Persuasion, and Pity. Perhaps fearing that they might possibly omit a god and thereby incur that one’s disfavor, the men of Athens had erected an altar inscribed with the words, “To an Unknown God.” At the outset in his discourse to the Stoics, Epicureans, and others assembled at the Areopagus (Mars’ Hill), Paul tactfully drew their attention to this altar, telling them that it was this God, heretofore unknown to them, about whom he was preaching.​—Ac 17:18, 19, 22-34.

That altars of this nature existed in Greece is testified to by the Greek writers Philostratus (170?-245 C.E.) and Pausanias (second century C.E.). Pausanias mentions altars of “gods named Unknown.” (Description of Greece, Attica I, 4) Philostratus, in his work The Life of Apollonius of Tyana (VI, III), writes: “It is a much greater proof of wisdom and sobriety to speak well of all the gods, especially at Athens, where altars are set up in honour even of unknown gods.”