Scholars debate whether the Israelites recognized only one God or worshipped only one God.
Reprinted with permission from The JPS Torah Commentary: Deuteronomy, published by the Jewish Publication Society.
Deuteronomy 4:32-40 touches upon the part played by Moses in the development of monotheism in Israel. For the sake of clarity it is important that we define the terminology that is used in discussing this issue. The term monotheism refers to the belief that there is only one God. It is sometimes contrasted with monolatry, namely "the worship of but one god when other gods are recognized as existing" (Random House Dictionary).
These terms figure in the following discussion because scholars debate whether Moses, when he first prohibited the worship of other gods, simultaneously proclaimed that they did not exist; in other words, whether he proclaimed the doctrine of monotheism or only monolatry.
Although Moses tells the Israelites in 4:32-35 and 39 that the events of the Exodus and Mount Sinai show that there are no gods but the Lord, that passage is the first in the Torah to make this point (see also 7:9). None of the narratives about those events in Exodus, nor any passage in Leviticus or Numbers, states that those events taught the lesson of monotheism. Deuteronomy 4:35 could be taken as implying that Israel realized this lesson as soon as the events occurred, but the earlier books do not support such an interpretation.
The book of Exodus frequently points out the lessons that were taught immediately by the events of the Exodus and Sinai, such as the fact that the Lord is incomparable and reliable and that Moses is an authentic prophet; nowhere does it say that the Lord is the only God. The laws of Exodus infer from those events only that Israel must not worship other gods; since laws do not normally deal with theological matters, they do not discuss the question of whether other gods exist.
From the perspective of the Torah, then, it could be argued that Moses may not have taught the full monotheistic implications of the Exodus and Sinai to the generation that experienced those events, but only to their children forty years later.
Monolatry, Not Monotheism
Many critical scholars think that the interval between the Exodus and the proclamation of monotheism was much longer. Outside of Deuteronomy the earliest passages to state that there are no gods but the Lord are in poems and prayers attributed to Hannah and David, one and a half to two and a half centuries after the Exodus at the earliest. Such statements do not become common until the seventh century B.C.E., the period to which Deuteronomy is dated by the critical view.