The present letter is not dated and it can only be said that it was written at some point during the episcopacy of Ambrose. Ambrose's addresee, Iraeneus, is treated with paternal affection. Irenaeus received several letters from Ambrose and is known only from this correspondence. He is never explicitely called a presbyter (or a cleric) and there is a scholarly discussion whether he actually was one - see especially Palanque 1933. That Irenaeus was a layman is claimed by Paredi 1968: 498 and Zelzer 1978: 15. He is considered a cleric by Mazières 1979 and later by Zelzer 1990: XXI, n. 6. See PCBE, Italie 1, Irenaeus 1.