Please refer to this post to understand where this post is going.
One of the thirteen principles of faith (of Maimonides) is that we need to accept that God wrote the Torah and that Moshe (Moses) recieved it from God on Mt Sinai. This all took place supposedly 3,500 to 3,300 years ago. Let us investigate the truth of this statement using nothing other than the Torah itself. No fancy archaeological findings or anything like that. Just using the Torah itself as a guide.
The arguments that are about to be presented are standard arguments that have been noticed by past philosophers. These will be arguments that Biblical skeptics use. I wish I can get the credit for this but it has been done by other people before. In particular, you can find this in more detail by reading Spinoza's "Theological-Political Treatise" or Paine's "Age of Reason".
Our approach here will be simple. We will consider the statement, "Moshe is the author of the Torah" by seeing how consistent it is with what we find in the Torah. If this statement is consistent it does not make it true (why not? well, just take the statement "humans have 600 bones", this statement is consistent with what we have in the Torah but it does not make it true). However if this statement is inconsistent with the Torah then it does not necessary make it false, it just means that both the Torah and the statement cannot be both correct, for example, the statement "there is no God" is inconsistent with the Torah, this does not make it necessarly false, it only means that both the Torah and the statement "there is no God" cannot be true simultaenously. Thus, if we can show that "Moshe is the author of the Torah" to be inconsistent with "the Torah is true and is from God given to Moshe" then it must mean that at least one of these statement is true. Any one of these statemens would immediately falsify Judaism. To falsify Judaism it is therefore sufficient to show the inconsistency of the statement "Moshe is the author of Torah" with the Torah itself. This is my favorite approach to discredit Judaism because it uses nothing other than Judaism's inconsistency to destroy itself. There is no need to jump to the scientific knowledge we have of the world today, this simple approach of using our own reason is good enough.
Third Person Perspective: The Torah speaks of the accounts of Moshe, as if he is being discussed by some other author. This is found throughout scripture everywhere (with the exception of Genesis). Just take the first sentence of Deuteronomy 1:1, "These be the words which Moses spoke unto Israel". If Moshe was the author would it not been proper to omit that passage or else to write, "These are the words which I have spoke onto Israel"? A believer would object to me saying that Moshe was only being formal. If he wrote "me" or "I" then he would have not been formal about writing the Torah. I agree this answer to the question raised would be satisfactory. However, the answer that Moshe is written in a third-person perspective for formality does not explain everything. It would explain the above question raised, and it would explain all the numerous "And God spake onto Moshe saying" verses. But in Deuteronomy 2:1, we find, "Then we turned, and took our journey into the wilderness by the way of the Sea of Reeds, as the Lord spoke unto me". This passage is written in first-person perspective. Moshe (supposedly) is saying his own journey and how God spoke with him. Why would Moshe not be formal and account this event like all the other events? Something different must going on here. The best answer that I can think of is that the original compilers of the Torah thought this passage was actually said by Moshe, so they kept it in first-person perspective while they narrated the rest of the Torah by describing Moshe in third-perspective. More importantly consider Deuteronomy 34:5 and 34:6 where it describes the death of Moshe in the land of Moab. If we are to accept that Moshe wrote the Torah and narrates it formally by speaking of himself in third-person (ignoring an exception to this rule when Moshe speaks about himself in first-person) then we have a serious problem. How can Moshe write about his own death? Clearly, if you find an autobiography about a death of the author then it cannot be an autobiography. This passage strucks severe blows to the idea that Moshe is the author. Another troubling one to a Jewish believer is in Deuteronomy 34:10, "there arose no prophet since in Israel like Moshe". This must be talking about after the death of Moshe. If a passage says that no other prophet was an equal of Moshe, it must be referring to after his death, furthermore this must be referring to long after his death. No person would say something like that immediately after Moshe died, a considerable amount of time must take place before one can say that. So not only does the Torah internally suggest that Moshe could have not written the Torah but it also shows that the Torah, whoever the authors were, must have written it after a considerable amount of time after the death of Moshe.
Since this exposition may be long, I will break it into several parts.