I was asked the titular question in response to my video retelling the Biblical account of the birth and death of Moses yesterday (on the date that is considered to commemorate both his birth and death, and from the land where he was born).
That video, before The Great Pyramid of Giza is here:
I responded:
Nothing is certain to us humans but the Bible's own claim is actually even stronger than that. It is that not only did Moses exist but that around 2 million people had some sort of divine "revelation" during which it was indubitably clear to them that Moses was receiving a direct transmission from God.
THAT, in fact, is the reason why the Israelites (Jews, Hebrews, whatever) accepted the Torah of Moses and why, later on, Christians did as well.
The Torah makes that claim explicitly. To wit, that millions of people had this revelation of God speaking to them (briefly) and then to Moses extensively.
In fact, Moses himself makes that claim before he died and tells future generations (like you and I) to ask whether any other nation has such a claim.
I recently published a video series on The 10 Commandments which you can find here: https://youtube.com/playlist?list=PL20zNTAn_sgc5vsXwXuBKLVD4HBFfTEfz&feature=shared
Videos 4 through 13 cover The Big 10.
Video 16 is an extended version of #6 "Thou Shalt Not Murder", while videos 1, 2 and 15 comprise the preamble and postscript.
Videos 3 and 14 however are the word for word story of The Revelation that encompass the 10 commandments, and, in fact, the reason WHY the Torah claims Jews ever accepted the 10 Commandments (and the rest of Moses' teachings) in the first place.
The Torah/Jewish claim for the existence and prophetic mission of Moses are explained IN THOSE VIDEOS, 3 and 14, which have Moses retelling the story of The Revelation.