The Achronim are leading rabbis from the 16th Century to the present.
I’m listening to a Torah in Motion lecture by Dr. Marc B. Shapiro wrapping up his series on German rabbi David Zvi Hoffman.
Rabbi Shapiro talks about a case where Rabbi Hoffman converted a non-Jewish woman who was living with a Cohen. He would not marry the woman to the Cohen (nor would any Orthodox rabbi). But he permitted them to live together with a civil marriage. She was the Cohen’s concubine (pilegesh) from the perspective of Jewish law.
Oy, here I am trying to learn some Torah and sex rears its ugly head.
Dr. Shapiro says that most rishonim said it was OK to live with a pilegesh as long as the laws of menstruation and the mikveh are followed. The Rambam disagreed but the Ramban was totally down with the concubine thing.
Dr. Shapiro calls David Zvi Hoffman the greatest Torah scholar of modern times and says that Rabbi Isaac Herzog had the greatest amount of secular and Torah learning of anyone since the Rambam. Rabbi Hoffman did not know music, philosophy, literature, art, etc. Rav Soloveitchik grew up in Eastern Europe and was an expert in philosophy and mathematics as was Rabbi Herzog who knew about ten languages and had a classical education (Greek, Latin, English Lit, Shakespeare, etc).