We possess in the book known as Ben Sira, or Ecclesiasticus,[67] an invaluable and easily dated record of life as it appeared to a cultured and wealthy inhabitant of Jerusalem about the year 200 B.C.E. The incidental references to past time and, above all, the inferences which may legitimately be drawn about the origins of a society so completely organized as that of Judea at that time, render recourse to the book a necessity at many points of our investigation. While accordingly we find it a convenient terminus in both directions, we must make large individual qualifications. Ben Sira does not fully represent his time or his people. He belonged to a definite social stratum. His own studies and reflections had no doubt developed conclusions that were far from being generally shared. But he is an eloquent and unimpeachable witness that the Biblical books had already reached a high measure of sanctity, and the division later perpetuated in the tripartite canon of Law, Prophets, and Writings, already existed; and, if nothing else, the single reference to Isaiah as the prophet of consolation renders it probable that even so heterogeneous a corpus as the canonical Isaiah was already extant much as we have it now.[68] Opinions may differ as to the length of time necessary to permit this development. But that a very few generations could have sufficed for it is scarcely credible. Since even the Secondary Canon, that of the prophets, had already become a rigid one, in which historical differences in parts of the same book were ignored, the Law must have been fixed for an even longer time, and the process of interpretation which every living code requires must have gone on apace for very many years indeed.