In 1874 he was appointed docent at the Lehranstalt für die Wissenschaft des Judenthums in Berlin, and in 1883, on the death of David Joël, he was called to the seminary at Breslau.
Lewy's knowledge of Talmudic literature was unusually wide; he was endowed also with an exceptionally acute and dispassionate critical spirit and with a faculty for grasping the proper importance of details.
His first publication was Ueber einige Fragmente aus der Mischna des Abba Saul (Berlin, 1876), in which he showed that the Mishnah collections of the foremost teachers in the period before the final redaction of the Mishnah itself, including that of Abba Saul, agreed as regards all the essential points of the Halakha.
Ein Wort über die Mechilta des R. Simon (Breslau, 1889) was likewise an authoritative work in the field of halakhic exegesis.
But his main proof was shown to be stemmed from a mistake and most sources point to the fact that both the order and the tractate where referred to as Nezikin.