For guidance in practical application of Jewish law, the majority of Orthodox Jews appeal to the Shulchan Aruch ("Code of Jewish Law" composed in the 16th century by Rabbi Joseph Caro) together with its surrounding commentaries. Thus, at a general level, there is a large degree of uniformity amongst all Orthodox Jews. Concerning the details, however, there is often variance: decisions may be based on various of the standardized codes of Jewish Law that have been developed over the centuries, as well as on the various responsa. These codes and responsa may differ from each other as regards detail (and reflecting the above philosophical differences, as regards the weight assigned to these). By and large, however, the differences result from the historic dispersal of the Jews and the consequent development of differences among regions in their practices (see minhag).
What do Orthodox Jews turn to for guidance and practical application of jewish law?
Shulchan Aruch