They were a unique product of rabbinism; and the authors of the system were also the compilers of its literary expression, the Talmud.
It was Christianity that preserved Jewish apocalyptic, when it was abandoned by Judaism as it sank into Rabbinism, and gave it a Christian character either by a forcible exegesis or by a systematic process of interpolation.
But after the fall of Jerusalem, partly through the need for systematizing the traditional post-biblical law, and partly through disputes with the Christians, orthodox Rabbinism received the stamp which has since characterized it.
His homiletic books, Epistle on Sanctity (Iggereth ha-qodesh) and Law of Man (Torath ha-Adam), which deal respectively with the sanctity of marriage and the solemnity of death, are full of intense spirituality, while at the same time treating of ritual customs - a combination which shows essential Rabbinism at its best.
One of the chief centres of Rabbinism was Safed, still a sacred city of the Jews and largely inhabited by members of that faith.