Imagine a researcher sitting in his lab doing all kinds of equations to try to determine what the best shape of a new airplane wing should be. While he is doing his research, an engineer is outside also working on the same goal by building test wings in a hanger and flying planes with test robots to see what will work. The engineer suddenly runs into the lab and tells the scientist that he discovered a great new wing design that is better than anything that has ever been invented. As he describes it, the researcher begins to scribble equations.
"Wait one second," the researcher interrupts. "There is no way that design can work. Just look here at my equations and you see that this is impossible..." and he continues scribbling away.
"But," stammers the engineer, "Forget your equations -- I built that wing and saw my model flying in the sky with it!"
When it comes to the mitzvah of emunah some people may think that we should start with philosophical analysis rather than rely on tradition. Their model is no less than the Rambam's Moreh Nevuchim. Isn't it strange that the great ba'alei machshava of the past few hundred years have all move away from this approach and in fact have discouraged this type of thinking? If we could philosophically prove that we are correct, wouldn't that be better than accepting our mesorah and leaving it at that?
The answer is of course not and all we need to do is think about our researcher and engineer to know why. No matter how much evidence there is for any fact, someone will always come along and debate the point or claim that the proof is insufficient. You can scribble and debate equations from today until tomorrow, but there is no proof better than a real flying airplane. If you see the plane in the air, you know the design works -- the fact that you may have a kashe on the equation does not change reality.
R' Tzadok haKohen (Sefer haZichronos, p. 53) writes that the Rambam only wrote what he did to fulfill "da mah she'tashiv" to the philosophers of the word. Had Aristotle been present at ma'amad Har Sinai, had Plato seen the man falling in the desert, had any great thinker seen kriyas yam suf, the be'er, etc., do you think they could even have a hava amina that Torah is not true? Of course not.
When you read all kinds of debates on blogs as to whether there is or is not evidence of Torah being given or all kinds of stuff, it's like a debate over whether the equation for the airplane wing will work. Torah committed Jews have been flying using these wings for thousands of years -- we know they work. When someone comes along and says ma'amad har Sinai did not happen, it's like the researcher saying, "You could not possibly have built that plane because my equation proves that it cannot exist". We know about ma'amad Har Sinai because we were there -- our parents heard about it from their parents and our nation has carried this story as part of its heritage for thousands of years.
Yes, there is an idea of "dah mah sha'tashiv" for those who have not seen the plane in flight, but that is no substitute and certainly no better than that which we know to be fact based on our historical experience. Nebach, some people forget the experiences of their roots and need to look elsewhere for validation, but that situation b'dieved does not a l'chatchila become.