The intense conservatism in religion for which they have become proverbial is fully confirmed by facts. There exists no other race of men that has approved its fidelity to religious conviction for an equal period, under equal difficulties, and amid equal temptations. Antiochus, Titus, Firuz, Reccared, Edward I. of England, Philip Augustus of France, Ferdinand of Spain, exhausted the resources of tyranny in vain to shake their constancy. Their power of resistance rose with the occasion that called it forth; and their fervid loyalty to the faith transmitted to them by the fathers never appeared to greater, advantage than when it cost them their peace, their happiness, and their life to maintain it. Since the close of the last century, however, a great change has apparently come over the Jewish people. Not only have they abandoned their former attitude of reserve and mingled freely with their fellow-citizens of whatever creed, not only have they taken a leading part in the great political revolutions that swept over Europe, but the passion for change, so characteristic of the age in which we live, has extended even to their time-honored religion; and a movement aiming at nothing less than the complete reformation of Judaism has arisen, and rapidly acquired the largest dimensions. The very fact that such a movement should exist among such a people is rightly interpreted as a sign of the times deserving of careful and candid consideration; and great interest has accordingly been manifested of late on the subject of Jewish Reform. In a series of articles we shall undertake to give a brief sketch of the origin and bearings of the movement. But before addressing ourselves to this task it will be necessary to review a few of the main causes that have enabled the Jews to perdure in history, and to consider the motives that impelled them to resist change so long, if we would properly appreciate the process of transformation that is even now taking place among them. Among the efficient forces that conduced to the preservation of the Jewish people we rank highest: THE PURITY OF THEIR DOMESTIC RELATIONS