Some Bible verses say that the Pentateuch was entirely written by Moses (cf. e.g. Ex 24:37; Deut 31:24). In these verses it is said that Moses wrote the “Law” or the “Words of this Law”. So for centuries the Catholic Church affirmed that the Pentateuch was written by Moses. But is this true?
It is possible that Moses wrote some laws, for example the Ten Commandments (Ex 20; Deut 5). It is possible that Moses wrote the words of the Ten Commandments on stone. It is also possible that Moses wrote the other laws following the Ten Commandments, the so called “Covenant Code” (Ex 20-23). But these laws don’t represent the entire Pentateuch that Moses would have written.
Answering to the question of Pentateuch’s authorship we need to take into consideration that the Pentateuch is not a single book. It is made of five books composed in places and times very different from one another. A second element is that it very difficult that Moses could have remembered the entire Israel’s History, from the Creation to the end of the desert’s journey. It is impossible that Moses wrote about his death and his burial! (cf. Deut 34).
Moreover the word “Law” has not the same meaning throughout the entire Pentateuch. It is said in Exodus that God ordered Moses to write the “Words” (i.e. the “Words of the Law” – Ex 34). Here the “words” are those of the Law, namely the words of the Ten Commandments, the Covenant Code and the Sanctuary Building’s Instructions. In Deuteronomy instead the word “Law” has a different meaning. It is the covenant that God made with his people of which Moses is the indisputed ruler. At that time – in the VI century BC – Moses was considered the founder of the Israelite religion and this was a very important element for the Jews that had been exiled in Babylon.
Moses wasn’t the author of the entire Pentateuch, but was the founder of the Israel religion. And usually the Sacred Books of a religion are ascribed to the Founder of that religion, even if the Founder lived many centuries before that the Sacred Books were effectively written!