http://www.biblicalarchaeology.org/reviews/the-fiscus-judaicus-and-the-parting-of-the-ways/ “[…] those who lived a Jewish life without publicly acknowledging the fact and those who concealed their Jewish origins. […] Heemstra argues that the first category includes gentile Christians (who lived a Jewish life without publicly acknowledging the fact) and the second includes Jewish Christians (ethnic Jews who concealed their Jewish origins).”