The Greek adjective agnōstos (ἄγνωστος) means unknown, not known, or unrecognized. It is the alpha-privative (a-) form of gnōstos (known), from ginōskō (to know). It appears most memorably in Acts 17:23, where Paul in Athens identifies an altar inscription reading "TO AN UNKNOWN GOD" (Agnōstō Theō) and declares: "What you worship as unknown (agnooūntes), I now proclaim to you." The word became the pivot of one of Scripture's greatest apologetic sermons.
The Athenian altar to an Agnōstos Theos (Unknown God) represents humanity's deepest theological intuition: there is more to ultimate reality than what we know. The Greeks hedged their religious bets — if we've missed a god, let this altar cover it. Paul seizes this intellectual humility as the door for the gospel. The God who was agnōstos — unknown, intuited but not revealed — has made Himself known in Jesus Christ, the one by whom He has "set a day when he will judge the world with justice" (Acts 17:31). Agnōstos is not just a Greek philosophical category; it is the human condition. John 1:10 carries the same tragedy: "He was in the world… and the world did not know (egnō) him." The Incarnation is God's answer to agnōstos — the unknown made known, the hidden revealed, the mystery made plain (Romans 16:26).