This classic of Jewish religious thought began as a critical essay vigorously challenging Adolf Harnack's "Essence of Christianity." It grew into a comprehensive examiniation of Jewish religion and an invaluable key to understanding the background of Christianity and Islam. since its first publication in 1922 it has gone through many editions and revisions until today it stands as a standard work in introspective religious literature.

Jewish tradition permits conflicting schools of thought to exist side by side, as well as a many-sided interplay of ceremonial law, philosophy, theology and mysticism. It has never been greatly concerned with formulating dogmas. It is therefore a major achievement to have succeeded in defining its essential ideas and doctrines. Baeck's presentation is based upon biblical, talmudic, and later rabbinical sources. It preserves the variety and fullness of these classical originals; it avoids dogmatism; yet to Judaism, with all its diversity, it has given a definitive formulation.