Believability

Sefer HaIkkarim (1:20:1) A thing perceived by an unusually popular and trustworthy person or by a number of persons of superior powers of comprehension or by an unusually large number of persons, is more likely to satisfy the mind of its reality and to be firmly believed than a thing not so accredited. For this reason God desired that the Torah should be given through Moses with great publicity and in the presence of a mighty multitude of six hundred thousand people. For according to the wise men of the Cabala this number includes all physiognomies, hence the publicity could not be greater, though the number of persons had been multiplied many times.

According to the Rabbis, the revelation was published before the whole world. Commenting on the verse, The Lord came from Sinai, and rose from Seir unto them; He shined forth from mount Paran …, they say, Why Seir and why Paran? The answer is, that God offered the Torah to all the world, who refused to accept it. Then Israel came and accepted it. The meaning is that since there were then seventy nations in the world and the text of the Bible mentions only Seir and Paran, it is clear that the reference is not to mount Seir and the wilderness of Paran, but to the whole world. Knowing that founders of religion were to arise in the future in Seir, i. e., the people of Edom and those associated with them, and in Paran, i. e., the people of Ishmael and those related to them,—two nations including the whole world, and both descended from Abraham, the first true believer, God published before these nations His revelation of the Torah to Israel, pointing out to them that the revelation of a divine law must be published very widely, else it is not divine. This is so because an order which passes between God and the prophet alone leaves a suspicion or doubt in the minds of others, even of those living in the same generation, not to mention those who come after. Thus even in the case of Moses, the Israelites did not fully believe in his prophetic character until the day of the revelation on Sinai, when they heard the voice speaking to him, as we saw before.

This is the reason why the Torah was not given completely to Abraham, Isaac or Jacob that they should command their children after them to keep the way of the Lord. For though the tradition should be handed down by them continuously from father to son, some suspicion or doubt might occur to those who came after in future generations, because those who received the law first were individuals. The case is different where the thing is clearly perceived by a very great number of persons embracing many wise and intelligent men, representing a great variety of opinions. This is the reason why the Torah was given through Moses with such great publicity, in order, namely, as I said before, that no suspicion or doubt should remain in the minds of the recipients and their associates, nor in the minds of those who come after, so that the tradition may be as firm and true as it is possible to make it.