Among our cognitive faculties — among our belief-forming mechanisms — is one that automatically forms belief in God under a wide-variety of circumstances.  It is what we might call a “God faculty,” or what theologians have called the sensus divinitatis, the “sense of the divine.” 

By seeing a majestic mountain range or the birth of their first child (just two of innumerable examples), many people just find themselves believing in God — or at least in something supernatural.