You're thinking a level too low. It isn't a question of 'is magic real'. The ability to alter reality by belief is something everyone possesses. The difference between an Awakened Mage and a 'Sleeper' is that the Mage's strength of belief and will is great enough to overwrite the reality everyone 'knows' exists with their own.

Think of it this way: 2+2=4, right? Well, Magick is being able to say "2+2=5" and have it be absolutely true, to some extent or another. But when you yank reality out of where everyone believes it to be like that, it backlashes in your face.