R. Kook argued that there is good reason to observe mitzvot even if one does not have a traditional view of the Torah’s authorship. On the one hand, there is nothing surprising in this. After all, would anyone tell a non-Orthodox Jew that it is OK if he eats on Yom Kippur? R. Kook’s originality is therefore not seen in the bottom line, but in the argument he uses. He notes that Maimonides and other medieval greats used arguments that they themselves did not accept in order to make religious points. For example, Maimonides used an argument that assumed the eternity of matter in order to prove the existence of God. This was valuable in that those who accepted the former point would also be forced to acknowledge the latter point, i.e., God’s existence. Only then could he attempt to weaken the belief in eternity. Similarly, R. Kook is prepared to argue for the binding nature of Torah law even on the assumption that it was not given to Moses. This is valuable since, in his day at least, it was the acceptance of biblical criticism that encouraged people to give up the observance of mitzvot. If R. Kook can therefore show that even an acceptance of biblical criticism does not mean that there is no place for mitzvot, it will be a great achievement.
R. Kook notes that traditional Jews observe rabbinic laws and even customs. His point is that these are regarded as valuable and help form the religious personality Yet no one believes that they were given to Moses by God. Why, then, should believers in biblical criticism not feel bound to other laws, which while traditionally seen as from Sinai, can also be regarded as rabbinic or even as customs (“folkways” in Mordecai Kaplan’s language). In other words, the mitzvot should be seen as having value regardless of their origin.