Rabbi Moshe Isserles (henceforth “the Rema”; 1525-1773, Krakow) is one of the best known Poskim (rabbinic adjudicators) of the last few centuries. His most famous achievement is his set of glosses to the Shulhan Arukh, which contributed immensely to securing the Shulhan Arukh as the most useful and important book of Jewish law of its era.
Despite the abundant material on the Rema that has accumulated over the last century, including Asher Ziv's monumental book “The Rema”, not much has been done to understand his modus operandi. The goal of this research is to examine how the Rema worked and what led him to his conclusions by looking at his library. We will explore which books were available to him and how he used them, the extent to which his work can be considered innovative and creative, and how far he can be considered a direct continuation of previous generations of Poskim in the Ashkenazi sector.