But this very development of Mosaism implies the existence of an original nucleus or substratum, although the recovery of its precise extent is very difficult.
For Amos and Isaiah were able to single out those loftier spiritual and ethical elements which lay implicit in Mosaism and to lift them into their due place of prominence.
They identify with Deuteronomy the law-roll which explains the noteworthy reforms of Josiah (§ 16); but since it is naturally admitted that religious conditions had become quite inconsistent with Mosaism, the conservative view implies that the " long-lost " Deuteronomy must have differed profoundly from any known Mosaic writings to which earlier pious kings and prophets had presumably adhered.
This again simply means that the Mosaism of Ezra or Nehemiah must have differed essentially from the priestly teaching prior to their arrival.
Still it remains true that the exclusive use of the argument from Mosaism, as itself implying the Gospel of Jesus the Christ as final cause (Taos), does favour the view that the readers were of Jewish origin.