Potter is mocked by a faculty member for the idea that there is evil in the world from which even children need to learn to defend themselves by the actual practice of doing so rather than familiarity with theory.
J. K. Rowling'Tell me one last thing,' said Harry. 'Is this real? Or has this been happening inside my head?' Dumbledore beamed at him, and his voice sounded loud and strong in Harry's ears even though the bright mist was descending again, obscuring his figure. 'Of course it is happening inside your head, Harry, but why on earth should that mean it is not real?'
J. K. Rowling