This chapter offers a Weber-inspired, sociologically informed account of the reception of the sciences and of rationalist philosophy by European Jews in the 12th-14th century. My main focus is on the appropriation of the sciences, the process through which the European Jewish cultures “imported,” integrated, and legitimized initially alien bodies of secular knowledge. The cultural tongue of European Jews was Hebrew and so I attend to the phases through which the Hebrew corpus of writings on science was constituted. (Space limits did not allow treating Jewish scholars’ own scientific activity, for which readers are referred to Science in Medieval Jewish Cultures of 2011.) The constitution of the Hebrew bookshelf of secular learning has to be considered separately for each of the three centers: Midi (“Provence”), the major center of cultural transfer; the Italian Peninsula; and Christian Spain. (In Ashkenaz and Tzarfat the reception of secular bodies of knowledge was virtually nil.) Another distinction is that between the appropriation of bodies of knowledge from Arabic and from Latin. Also, the reception of knowledge in the sciences (astronomy, astrology, mathematics, natural science, psychology, etc.) and in medicine have to be discussed separately, the respective social processes having been different: e.g., in the Midi, the scientific bodies of knowledge originated mainly in Arabic culture with little input from Latin, while in medicine the reception from Arabic was gradually complemented by a reception from Latin. In the Italian peninsula, however, small scientific-philosophical bodies of knowledge were smoothly transferred from Arabic into Hebrew, contrasting with the virtual absence of parallel processes in the Midi. A number of literary genres are considered: works written by Arabophone scholars in Hebrew and discussing scientific matters (Maimonides’s Book of Knowledge is a major instance); so-called “encyclopedias” written in Hebrew by Arabophone scholars with the aim of offering their brethren a “digest” of significant bodies of knowledge; and, above all, Hebrew translations (essentially from Arabic) of significant works. I present some of the authors and translators engaged in this massive cultural transfer and discuss their motives. I also offer some statistics about the distribution of Hebrew translations according to disciplines, source language, and centuries. The distinctive sociological characteristic of the Arabic/Latin-into-Hebrew translation movement is that it was entirely decentralized: the translated bookshelf resulted from a large number of uncoordinated grass-roots initiatives by many authors, patrons, and translators, who wrote and translated texts according to their own agendas and preferences. In this respect, the cultural transfer into Hebrew cultures contrasts with the Greek/Syriac-into-Arabic and Arabic-into-Latin translation movements, both of which were initiated and sustained by political authorities and were centrally coordinated. We have to do here with a notable cultural change within Judaism. It began before Maimonides, but the latter’s new religious ideal made the study of the sciences and of philosophy into a religious obligation. Maimonides gave the Jewish appropriation of “alien wisdom” a crucial theological and halakhic legitimization and, thusly, a crucial impetus. Nonetheless, Maimonides’s charismatic authority notwithstanding, the great majority of Jewish intellectuals continued to give absolute priority to Tradition and remained reserved or hostile to the rationalist religious ideal. Consequently, as a rule, science was not institutionalized and remained the province of isolated individuals. This goes a long way toward explaining why science did not take off in medieval Jewish cultures. The bottom-line is that, globally, Jewish culture was a consumer rather than a producer of scientific knowledge. The Jewish engagement with science in Europe is more a part of Jewish cultural history than of the history of science.