It had so fallen out, even before the exile, that the reform of the theocracy which the prophets demanded began in the cultus; and after the exile this tendency could not fail to be persisted in.  The restoration of Judaism took place in the form of a restoration of the cultus.  Yet this restoration was not a relapse into the heathen ways which the prophets had attacked.  The old meaning of the festivals and of the sacrifices had long faded away, and after the interruption of the exile they would scarcely have blossomed again of themselves; they had become simply statutes, unexplained commands of an absolute will.  The cultus had no longer any real value for the Deity; it was valuable only as an exercise of obedience to the law.  If it had been at first the bond connecting Israel with heathenism, now, on the contrary, it was the shield behind which Judaism retreated to be safe from heathenism.  There was no other means to make Judaism secure; and the cultus was nothing more than a means to that end.  It was the shell around the faith and practice of the fathers, around the religion of moral monotheism, which it alone preserved until it could become the common property of the world.  The great public worship gave the new theocracy a firm centre, thus keeping it one and undivided, and helped it to an organisation.  But of more importance was the minor private cultus of pious exercises, which served to Judaize the whole life of every individual.  For the centre of gravity of Judaism was in the individual.  Judaism was gathered from scattered elements, and it depended on the labour of the individual to make himself a Jew.  This is the secret of the persistence of Judaism, even in the diaspora.  The initiatory act of circumcision, which conferred an indelible character, was not the only safeguard; the whole of the education which followed that act went to guard against the disintegrating effects of individualism.  This is the real significance of the incessant discipline, which consisted mainly in the observance of laws of purity and generally of regulations devised to guard against sin.  For what holiness required was not to do good, but to avoid sin.  By the sin and trespass offerings, and by the great day of atonement, this private cultus was connected with that of the temple; hence it was that all these institutions fitted so admirably into the system.  The whole of life was directed in a definite sacred path; every moment there was a divine command to fulfil, and this kept a man from following too much the thoughts and desires of his own heart.  The Jews trained themselves with an earnestness and zeal which have no parallel to create, in the absence of all natural conditions, a holy nation which should answer to the law, the concrete embodiment of the ideals of the prophets.