Menocal concentrates on the achievements of the three communities in establishing written vernacular languages, preserving and disseminating Greek learning, advancing scientific and philosophic knowledge, and developing literary forms in Castilian, Arabic, and Hebrew. I find particularly interesting her exploration of the combination of secular and religious thought that developed in both Christian and Muslim enclaves, and subsequently was destroyed by religious fanaticism.
She writes, for example, of the Jews of Cordova in the twelfth century:
"The Jews understood themselves to be Andalusians and Cordobans, much as the German Jews of the late-nineteenth century -- Marx and Freud most prominent among them -- considered themselves Germans, or the American Jews in the second half of the twentieth century, who helped define the intellectual and literary qualities of their time, never thought twice about calling themselves Americans. But unlike many later European and American Jews, the Andalusian Jews had not had to abandon their orthodoxy to be fully a part of the body politic and culture of their place and time. The Jews of al-Andalus wre able to openly observe and eventually enrich their Judaic and Hebrew heritage and at the same time fully participat in the general cultural and intellectual scene. They could be the Cardozas and the Trillins [I fear that she means Lionel, not Calvin Trillin] and the Salks of their times because they were citizens of a relilgious polity -- or tather, of this particular religious polity. The Umayyads ... had created a universe of Musllims where piety and observance were not seen as inimical to an intellectual and 'secular' life and society." (p. 86-87)
She documents this duality of religious and secular thought and intellectual activity, as well as the political struggles between Islamic groups with different commitments to tolerance or intolerance, and then the fossilization of Christian thought that ended in the expulsion of Jews and Muslims and the totalitarian rule of the Inquisition. "As time went by," she wrote, "there was a growning sense of the showdown between faith and reason, to put the matter at its most blunt and simplistic..." (p. 207)
Judah Halevi, whom I wrote about a few days ago, was an important focus for some of her thoughts, as he participated in the most idealized environment for the combination of faith and philosophy, and wrote The Kuzari as a dialog exploring where this duality could lead. Then, of course, he concluded that his religious commitment could only require him to leave the open atmosphere of his home, which he found corrupting, and seek a different world by going to Jerusalem.
Menocal's book contains much more than I can possibly say here. The history of Convivencia (the name often given to the tolerant and open atmosphere of medieval Iberia, which disappeared when Ferdinand and Isabella created a united, monolithic Spain) is fascinating in its own right, not just because of its parallels to modern times, including the vexing question of Christianity vs. Islam or of the role of Jews in a non-Jewish society.