Proof of G-d's existence

 Ksav v'HaKabbala(Shemos 33:19): Clear logical proofs that G‑d exists were already known to Moshe Rabbeinu either on his own or from tradition or G‑d Himself informed him as the Rambam notes (Moreh Nevuchim 1:63) that G‑d showed Moshe all the intellectual proofs that would convince the sages. However it is universally agreed – even the great philosophers of the world concede this point – that all the logical proofs concerning G‑d's existence are imperfect and weak. … All the things which we accept as truly existing are material objects that we can detect with our physical senses. Accordingly it is appropriate to find causal links between those things that we perceive with our senses and say that something is the cause and something else the effect. However we don't look for an immaterial or intellectual construct as the cause…. According to this even if we accept the Rambam's view that Moshe knew all the logical proofs that G‑d exists and that He is a unity and that there is no other deity and even if we accept that Moshe taught the people all these proofs – nevertheless when it happened that some of the Jews greatly erred and sought out a false god – all the intellectual teaching that they had received did not help them concerning G‑d's true unity. Therefore [after the sin of the Golden Calf] Moshe now asked from G‑d to show him His Glory. Moshe wanted to understand and comprehend the true reality of His existence in the world with intellectual proofs that were far beyond the grasp of the ordinary intellect. In other words he wanted an intellectual comprehension which transcended a grounding in physicality and the senses. He wanted an abstract proof which needed no reference to common physical reality experience. This understanding of the Rambam can readily be seen in the various writings of the Rambam even though he doesn't say it directly…