The first five books of the Bible—known by Jews as the Torah and by Christians as the Pentateuch—are traditionally attributed to Moses.
But since the mid-1600s, scholars have been raising doubts about Mosaic authorship. In the 1651 book Leviathan, Thomas Hobbes gave examples of passages that indicated they were written long after Moses' time.
We read in the last Chapter of Deuteronomie, Ver. 6. concerning the sepulcher of Moses, "that no man knoweth of his sepulcher to this day," that is, to the day wherein those words were written. It is therefore manifest, that those words were written after his interrement. For it were a strange interpretation, to say Moses spake of his own sepulcher (though by Prophecy), that it was not found to that day, wherein he was yet living. But it may perhaps be alledged, that the last Chapter only, not the whole Pentateuch, was written by some other man, but the rest not: Let us therefore consider that which we find in the Book of Genesis, Chap. 12. Ver. 6 "And Abraham passed through the land to the place of Sichem, unto the plain of Moreh, and the Canaanite was then in the land;" which must needs bee the words of one that wrote when the Canaanite was not in the land; and consequently, not of Moses, who dyed before he came into it. Likewise Numbers 21. Ver. 14. the Writer citeth another more ancient Book, Entituled, The Book of the Warres of the Lord, wherein were registred the Acts of Moses, at the Red-sea, and at the brook of Arnon. It is therefore sufficiently evident, that the five Books of Moses were written after his time, though how long after it be not so manifest.
Philosopher Baruch Spinoza examined these passages and others—such as Genesis 36, which gives a list of Edomite kings going far beyond Moses' lifetime; Genesis 22:14 which refers to Mount Moriah, a name that wasn't given until the Temple was dedicated in Solomon's time; Numbers 12:3, which calls Moses the most humble man on earth (and, for that matter, the general fact that Moses is referred to in the third person throughout the Torah)—and was left with the conclusion that Moses may have written the core legal texts of the Pentateuch, but a later author (or several authors) had added most or all of the narrative. He suggested Ezra as the one who ultimately brought the whole text together.
Spinoza concluded that the Mosaic core can be found in two places: first, a set of laws referred to in Exodus 24 as the Book of the Convenant, and second, a fuller compilation of laws referred to in Deuteronomy as the Book of the Law of God.
Moreover, Exodus 24.4 and 7 gives evidence of another book, called ‘The Book of the Covenant’ which Moses read out to the Israelites when God ¢rst entered into the covenant with them. This book, or letter, contained very little: simply the laws, or commands of God which are set out in Exodus from ch. 20.22 to ch. 24, as no one will deny who reads the chapter cited above impartially and with an ounce of sound judgment. According to that chapter, as soon as Moses understood the feeling of the people about entering into a covenant with God, he immediately wrote down the pronouncements and laws of God, and in the ¢rst light of morning, after completing certain ceremonies, read out to the assembled multitude the conditions for entering into the covenant. When he had ¢nished reading these and the multitude had understood them, the people bound themselves to themwith full consent. From the shortness of the time in which it was written and from its purpose of making the covenant, it follows that this book contained nothing but the few things just mentioned.
It is evident finally that in the fortieth year after the exodus from Egypt Moses expounded all the laws he had made (see Deuteronomy 1.5), and renewed the people’s commitment to them (see Deuteronomy 29.14); he then wrote a book which contained the laws he had set out and the 123 new covenant (see Deuteronomy 31.9). This book was entitled ‘The Book of the Law of God’ and is the book that Joshua subsequently expanded by adding the account of the people’s renewal of the covenant again in his day, when they entered into covenant with God for the third time (see Joshua 24.25-6).
In the mid-18th century, French physician Jean Astruc attempted to use the tools of source criticism to defend the idea that Moses was the author of the entire Pentateuch. What he found as he scoured the text changed his mind. In a book published anonymously in 1753, Astruc identified several "doublets" that appeared to be similar stories from two different perspectives. In these doublets, one story consistently uses the divine name "YHWH", while the other refers to God as "Elohim". Some examples:
Astruc's conclusion was that Moses adapted two streams of oral tradition and wove them into a seamless narrative.
Other scholars followed Astruc's lead and identified other types of doublets.
The presence of these doublets gave added support to the notion that the Pentateuch was the work of multiple authors. Johann Eichhorn of the University of Jena in Germany named these sources "J" for Jahwist (German Jahwist = English Yahwist) and "E" for Elohist, and outlined the first version of what would become known as the documentary hypothesis. But Eichhorn's work was just the tip of the iceberg.