Under rabbinical law, a modern-day gentile is required only to observe the Seven Laws of Noah, while Jews are bound by Mosaic law. In periods of decreased animosity between Jews and gentiles, some of the rabbinical laws against fellowship and fraternization were relaxed; for example Maimonides himself was a physician to the Sultan. Even though most rabbinical schools do not teach the same hostility as Middle Age rabbinical teachings, some Orthodox rabbinical schools hold extreme conservative views. For example, scholars from the Zionist HaRav Kook yeshiva are schooled in the doctrine that Jews and gentiles have different kinds of souls. One of the yeshiva's scholars, David Bar-Hayim, published a paper in 1989 explaining the doctrine, entitled "Yisrael Nikraim Adam" (Jews Are Called 'Men'). In his conclusion, Bar-Hayim writes: