In the Torah we read a passage that we recite daily in our morning prayers. When Bnei Yisrael crossed the see and the Egyptians were destroyed the Torah says that Bnei Yisrael saw the powerful hand of Hashem and VAYA’AMINU BASHEM UVEMOSHE AVDO, “they believed in Hashem and in his servant Moshe.” Did they not believe in him before?
The answer is that there are different degrees of believing. I can believe in something because my intellect tells me that it has to be so. I can also believe in something because someone tells me it is so. I can believe in something because I see evidence of it with my own eyes or my own ears.
Before the Jews crossed the sea they believed in Hashem based on what Moshe told them. They believed because they saw the plagues visited upon the Egyptians. At the sea they saw such a great miracle when the Egyptians were destroyed it was as if they were actually able to see Hashem. This belief was not based on intellect or on what they were told. This was due to what they saw and heard with their own eyes and ears.
When we see evidence of something we have to be alert enough to be able to recognize its meaning and to understand what we are really seeing.