משה רבינו לא האמינו בו ישראל מפני האותות שעשה. שהמאמין על פי האותות יש בלבו דופי שאפשר שיעשה האות בלט וכשוף. אלא כל האותות שעשה משה במדבר לפי הצורך עשאם. לא להביא ראיה על הנבואה. היה צריך להשקיע את המצריים קרע את הים והצלילן בתוכו. צרכנו למזון הוריד לנו את המן. צמאו בקע להן את האבן. כפרו בו עדת קרח בלעה אותן הארץ. וכן שאר כל האותות. ובמה האמינו בו במעמד הר סיני שעינינו ראו ולא זר ואזנינו שמעו ולא אחר האש והקולות והלפידים והוא נגש אל הערפל והקול מדבר אליו ואנו שומעים משה משה לך אמור להן כך וכך. וכן הוא אומר פנים בפנים דבר ה' עמכם. ונאמר לא את אבותינו כרת ה' את הברית הזאת. ומנין שמעמד הר סיני לבדו היא הראיה לנבואתו שהיא אמת שאין בו דופי שנאמר הנה אנכי בא אליך בעב הענן בעבור ישמע העם בדברי עמך וגם בך יאמינו לעולם. מכלל שקודם דבר זה לא האמינו בו נאמנות שהיא עומדת לעולם אלא נאמנות שיש אחריה הרהור ומחשבה:
The Jews did not believe in Moshe, our teacher, because of the signs he performed. For one who believes [in anything] because of signs has a blemish in his heart since it is possible that a sign was done through trickery and magic (and this person's faith is reliant on a fallacy). Rather, all the signs that Moshe performed in the desert were done out of necessity. [They were] not done to bring proof [as to the validity] of his prophecy. It was necessary to drown the Egyptians, so the sea was split and they were dunked in it. We (the Jews) needed sustenance so the manna was brought down [from the sky] for us. They (the Jews) were thirsty so the stone was split [and water came forth] for them. The congregation of Korach rebelled against [Moshe] so the earth swallowed them. And so too by all the other signs (miracles).
What is the reason we believe in [Moshe's prophecies? Because of] the events at Mt. Sinai that our eyes saw them and not a strangers [eyes] and our ears heard them and not another's [ears. These events were] the fire, the sounds (thunder, voices?), the lightning, and then [Moshe] approached the fog and the voice [of G-D] spoke to him and we heard "Moshe, Moshe, go and say to them such and such." And so he said, "Face to face G-D spoke with you." And so it says (devarim 5:3), "G-D did not make this covenant with our fathers."
From where [do we know] that the events at Mt. Sinai, in and of themselves, are a proof to [Moshe's] prophecy that [we should believe] it has no faults? For it says (Exodus 19:9), "Behold, I am coming to you in the thick cloud in order that the nation will hear when I speak to you and also that they will believe in you forever." This implies that before this [event, the Jewish people] did not have a belief in [Moshe] that would last forever, rather it was a belief that was speculation and apprehension.
This idea that the Rambam brings down is of critical importance. Signs, wonders and miracles are completely WORTHLESS when it comes to having a belief in anything. Jesus stood on water, the Baal Shem Tov flew across the world, and so on. These "miracles" have nothing to do with a JEWISH belief in G-D. The ONLY reason a Jew should believe in G-D is because of eyewitness proof. Just like I know my parents exist because I am an eyewitness, or I know president Obama exists because other people have told me he does and I see him on television. This is the Jewish belief in G-D, it is not some she said he said confusion, it is based on actually witnessed events.
This is the basis for the Rambam's belief in G-D, that this event at Mt. Sinai actually happened. It isn't something that occurred in a dream or was verified through "miracles," it was based on an event in reality that can be substantiated.