Diapason

This reply is about a year late, but here it is for whatever it is worth. My experience is with the Near Eastern Languages department at Harvard. Though many of the 'luminaries' of the past are now gone, don't underestimate Heinrichs. He is a giant in the field. His credentials are impeccable, as is his Arabic - his knowledge of Arabic is, quite simply, unsurpassed. He has directed many dissertations over a wide range of fields and subfields - though not the main advisor (Mahdi was), Heinrichs was one of the readers on Zysow's dissertation. He is an extraordinarily scrupulous principal advisor (and as a reader, as well), and little things (and things not so little) that will slip past any other advisor are unlikely to get past him. Though rather self-deprecating, he is, without question, a polymath. As for having a 'passing interest' in usul al-fiqh, it is perhaps worth noting, here, that his habilitationschrift (the dissertation submitted for the second doctorate in the German system) was on that very subject. Though he is most often associated with the field of classical Arabic literary theory, it is perhaps worth noting also that there are many points of intersection between Arabic literary theory and Islamic legal theory (most of the classcical literary theorists were also jurists or legal theorists, and their interest in literary theory was not just a passing one).