"The most important fact of the Middle Ages was the rise of Islam. . .. In the thought of the Prophet of Islam as revealed in the Quran and the Hadis (the Prophet's conversations sic) two basic ideas stand out—the principle of unity in the cosmic order and the principle of the brotherhood of those who believed in (the Prophet's) creed. Islam wrought one of the most vital and the most bloodless revolutions in human history. ... Medina under the Prophet was a working-class republic. . . . There was no governing class and no subject people."