We encounter Paul trying to culturally adapt Christianity to the greek religiosity. He tries to get fancy and creative by incorporating something they know and relating it to Christ.
The unknown god rises to the front in hopes that the people might come out of the darkness and into the light, to stop worshiping the unknown and embrace what is most known.
The greek word for unknown used in the reading entails two realities; it envisions an unknown reality because it has been forgotten.
It is interesting to note that Paul uses this analogy to tie in with Christ. For it is only in Christ that God is truly known. In fact God goes to a great extent just be known; he embraces the cross, stretched upon the wooden beam, in hopes that people might at last come to know just what love will do to offer life to the other.
The word, "unknown" and "forgotten" is the greek word form which we get the term "agnostic."
People who claim to be agnostic do so though they stare Christ in the face. We pray that they may be awaken from their forgetful slumber and come to know and thus come to love and no longer grope in the darkness and truly reach forth and touch the god who bears our flesh all the way to the Father.