Of the three monotheistic religions of the Semites, Islam was the last to make its appearance upon the stage of history in the third decade of the seventh century. Unlike its two predecessors, Judaism and Christianity, its appearance was attended by a series of epochmaking events which mark the eclipse of the two great empires of the time, Byzantium and Persia. And, whereas the beggign nings and developpm ent of the two latter religions are surrounded by comparative obscurity, historians know almost all the significant stages in the rise and development of Islam, which forces itself, like a cataclysm, upon the attention of the civilized world by dint of military prowess.