 Mechthild Gretsch describes Israel as " one of the most learned men in Europe " , and Lapidge says that he was " an accomplished grammarian and poet , and one of the few scholars of his time to have first @-@ hand knowledge of Greek " . Greek scholarship was so rare in western Europe during this period that in the 870s Anastasius the Librarian was unable to find anyone competent to edit his translation of a text from Greek , and had to do it himself . Israel wrote on theology and collected works of medicine . In the 940s he became interested in the Irish philosopher John Scottus Eriugena , and commented on his works in a manuscript which survives in Saint Petersburg . In a manuscript glossing Porphyry 's <unk> , he recommended John 's <unk> . His redaction of a commentary on Donatus 's Ars Minor was a major teaching text in the Middle Ages , and still in print in the twentieth century . 
