Norbert Baumert, «'Epi-gnosis' bei Paulus 'Eifer der Juden' - ohne 'Erkenntnis'? (Röm 10,2)», Vol. 22 (2009) 133-148
There is 'consensus' that the composed words epigignoskein / epignosis would be synonymous with the simple gignosko / gnosis in the sense of 'to know'. But the preposition epi always indicates a special connotation, e.g. 'clear, fully or 'additional knowledge'. In the three cases in which it appears in Rom, the sense is the following: in Rom 1,28 underlines, after what has been said in Rom 1,18-27, that there is a clear natural knowledge of God and therefore also knowledge of good and evil. Rom 3,20 says that God gave by the Law an additional knowledge of sin. Finally Rom 10,2 says that the Jews have religious zeal, but not in the sense of that additional knowledge that is now given in Christ. So Paul does not say they would have no knowledge at all, but only that they have not got this specific additional knowledge (German: Zu-Erkenntnis)1.