EXOD353 It is a positive commandment to believe that there is a God in existence as Scripture states [this verse]; and He--be He blessed and exalted--brought all existing entities into being, and all the world, by His power and blessed wish. It is He who watches over everything. This is the foundation of our faith, and whoever does not believe this denies the very main principle [the one and only God], and he has no share or right among the Jewish people. We are duty-bound to be ready to give our life and our might and main for this belief. The main thing, though, is to fix firmly in one's heart and soul that this is the truth, and nothing other than this is possible.