Who wrote the first five books of the Bible?
To get to the point, the answer is Moses, but since there are skeptics, I will give proof that Moses wrote the Pentateuch. First, to the argument, that "the vast majority of main-line scholars do not believe that Moses personally wrote the Pentateuch." The majority of main-line scholars do not even believe in the "inspiration" of the Bible. The idea of doubting Moses authorship has been around for 300 years.
Actually for those who are unbiased when it comes to the word of God, it is clear. It is argued that Genesis 14:14 mentions the Israelites region of Dan, which was assigned to that tribe during the conquest led by Joshua after Moses died. So Moses could not have written this verse. True, Genesis 14:14, does mention Dan. However, Dan in this context is not the region of Dan that the Israelite tribes inherited when the Jews took the Promised Land, but a specific ancient town of Dan north of the Sea of Galilee that was in existence long before the Israelites entered the land.
Also it is argued that the author of Genesis 30:31 obviously knew about kings in Israel, which took place well after Moses, so Moses could not have written this. But such a claim is without warrant. Moses was clearly aware that this had been prophesied about the nation of Israel when the Lord told Abraham (Genesis 17:6) and Jacob (Genesis 35:11) that Israel would have kings. Also, Moses himself prophesied in Deuteronomy 17:14-20 that Israel would have kings. So knowing kings were coming was already common knowledge to Moses.
Consider also what Jesus says about the authorship of the Pentateuch. Mark 12:26: "But regarding the fact that the dead rise again, have you not read in the book of Moses, in the passage about the burning bush, how God spoke to him, saying, "I am the God of Abraham and the God of Isaac and the God of Jabcob." Then beginning with Moses and with all the prophets, He explained to them the things concerning Himself in all the scriptures. John 5:46: "For if you believed Moses, you would believe Me, for he wrote about Me." There are more passages I could give from the New Testament, but notice I chose only a few from Jesus Himself. Can we trust Jesus, as to know for sure who wrote the first five books of the Bible?
Skeptics have been undermining the credibility of the Bible from its foundations for centuries. Just as Jesus said to Nicodemus in John 3:12, "If I told you earthly things and you do not believe, how will you believe if I tell you heavenly things? People have been taught that the Bible cannot be trusted at its foundations in Genesis; so they have little reason to trust the gospel message that stems from that foundation.