I’ll try to explain what I mean. Once one believes in God, it is also reasonable to believe in the Torah and in the revelation at Mount Sinai (as you’ve written in many places). Once all that is in place, the question is how much we rely on the Oral Torah and on the Sages. The question of whether they invented things on their own or received them by tradition is not a psychological question of probing the depths of the Sages’ minds (correct me if I’m wrong). The question is, as I understand it, one that belongs to historians: is the tradition we received accurate? Is there reason to assume there were breakdowns in the chain of transmission through the generations?
I thought the Rabbi hadn’t dealt enough with this area (correct me if I’m wrong), and so it seems to me like unnecessary skepticism. Especially since serious people said that belief in these matters is among the fundamentals. Of course, you aren’t very impressed by ad hominem arguments or by principles of faith, but still—these are serious people like Maimonides, Nachmanides, and other medieval authorities, whom you don’t dismiss when learning a Talmudic topic. Obviously you aren’t bound by them, but without sufficient reason it doesn’t sound reasonable to me to cast doubt on them.

If the World to Come were written in the Torah, there would be certainty.
At least if it were in the Prophets or the Writings, there would also be certainty.
But it isn’t written…
We have it from the Sages.

1. Did they say it on the basis of reasoning?
2.
Did they have a tradition that wasn’t written down but was passed on orally?
3.
Did they say it through divine inspiration?

If it’s based on reasoning, fine—but the fact that it isn’t written, doesn’t that itself weaken the reasoning a bit?
A transmitted tradition—again, why wasn’t it written? How rigid, precise, and reliable can something unwritten be?
After all, from the giving of the Torah until their time about 1,500 years passed.
And it’s also not clear when exactly the Mishnah and the Talmud were written down (edited in Rabbi Judah the Prince’s time—but when were they written? A dispute.)
Divine inspiration? You’d have to assume they had it, and again—why wasn’t it already in the prophets of the Hebrew Bible?

Moti,
There is no agreement among Jewish thinkers regarding the nature of the World to Come. The World to Come that Maimonides and his camp describe is not the World to Come that the kabbalists and their camp describe. All of this is based on philosophical judgment, so what is the problem with assuming that this whole topic arose from reasoning in the first place?
And in general, in the Bible there is, for example, no real reference to the World to Come (in the sense of a place of reward), and it’s not even clear that this is anyone’s concern.

I don’t care what the World to Come looks like. What bothers me is that the Rabbi casts doubt on there being any kind of life after death without sufficiently strong arguments, in my opinion. The Sages write many times that there is a World to Come; they interpret verses that way and explain many things based on the assumption that there is a World to Come, for example: “Happy shall you be in this world, and it shall be good for you in the World to Come,” and many more like that.
The way Maimonides tried to prove things is often no longer relevant today—even some of the proofs for God’s existence, for example “who moves the spheres…” But Maimonides believed in the World to Come because that is what he received in the tradition of the generations, and he treated it as a principle of faith such that one who does not believe in it has no share in the World to Come. That is a strong statement that requires anyone who challenges him to bring strong evidence. And likewise with Nachmanides and other medieval authorities.
The fact that in the Bible there is no direct treatment of the World to Come is a good question, and of course it poses a difficulty for the words of the Sages. But there are not-bad explanations for that. Still, the main point is that this belief was accepted throughout the generations of the Jewish people—at least those who survived. It takes courage and conclusive evidence to disagree with that. To me it sounds a bit too bold to dispute this principle of faith.

Maimonides subordinated the entire Torah to Aristotle’s doctrine. His World to Come is derived from his Aristotelian belief. He believes in it because of his intellect, and only afterward found support for it in the Torah.
The proof is that beliefs such as demons he rejected without any problem.

Maimonides preferred to find rational sources of information for his beliefs rather than relying on tradition, as he writes explicitly; from his perspective that was the best way to arrive at any information. Of course, he also received these things by tradition—there is no reason to think otherwise; he is no different from the other medieval authorities.
In any case, your remarks are not relevant, because when he turned certain beliefs into principles, that came from an understanding of the Torah that whoever does not believe in them has not accepted the religion of Israel. Turning a belief into a principle obviously does not come from an Aristotelian worldview. 50

That is not correct. All of his principles are full of Aristotelian beliefs. In fact, these are rational or Aristotelian principles/conceptions, and true belief in them actually constitutes the attainment of intelligibles, through which a person merits the World to Come. Most people nowadays quote only the headline and do not get into what exactly each principle means.