The Prophetic Spirit.
It was the prophetic spirit of the Jewish nation embodied in Abraham (not the Midianite, as Budde thinks, nor some Babylonian tribe, as the Assyriologists would have it) which transformed Yhwh, an original tribal deity localized on Sinai and connected with the celestial phenomena of nature, into the God of holiness, "a power not ourselves that maketh for righteousness," the moral governor of the world. Yet this spirit works throughout the Biblical time only in and through a few individuals in each age; again and again the people lapse into idolatry from lack of power to soar to the heights of prophetic vision. Only in the small Judean kingdom with the help of the Deuteronomic Book of the Law the beginning is made, and finally through Ezra the foundation is laid for the realization of the plan of "a kingdom of priests and a holy nation."
But while thus the people were won, and the former propensity to idolatry, the "yeẓer ha-ra'," was banished forever by the power of the men of the Great Synagogue (Yoma 69b), the light of prophetic universalism became dim. Still it found its utterance in the Synagogue with its liturgy, in the Psalms, in the Books of Jonah and Job, in the Books of Wisdom, and most singularly in the hafṭarah read on Sabbath and holy days often to voice the prophetic view concerning sacrifice and ritual in direct antagonism to the Mosaic precepts. Here, too, "the Holy Spirit" was at work (see Inspiration; Synagogue). It created Pharisaism in opposition to Sadducean insistence upon the letter of the Law; and the day when the injunction "an eye for an eye, and a tooth for a tooth" was abrogated, and the rationalistic interpretation of the Scribes was substituted therefor, was celebrated as a triumph of reason (Megillat Ta'an. iv. 1). While the legalists beheld God's majesty confined to "the four ells of the Halakah" (Ber. 8a), the Haggadah unfolded the spirit of freedom and progress; and when mysticism in the East threatened to benumb the spirit, philosophy under Arabian influence succeeded in enlarging the mental horizon of Judaism anew.
Thus Judaism presents two streams or currents of thought ever running parallel to each other: the one conservative, the other progressive and liberal; the one accentuating the national and ritualistic, the other the cosmopolitan and spiritual, elements; mysticism here and rationalism there, these together forming the centripetal and centrifugal forces of Judaism to keep it in continuous progress upon its God-appointed track.
Judaism, parent of both Christianity and Islam, holds forth the pledge and promise of the unity of the two ("Yad," Melakim, xi. 4; "Cuzari," iv. 23; see Jew. Encyc. iv. 56, s.v. Christianity), as it often stood as mediator between Church and Mosque during the Middle Ages (see Disputations and Judah ha-Levi). In order to be able to "unite all mankind into one bond" (New-Year's liturgy and Gen. R. lxxx viii.), it must form "one bond" (Lev. R. xxx.). It must, to use Isaiah's words, constitute a tree ever pruned while "the holy seed is the substance thereof" (Isa. vi. 13); its watchword being: "Not by might, nor by power, but by my spirit, saith the Lord of hosts" (Zech. iv. 6).