The Birth of Tragedy

Nietzsche wrote The Birth of Tragedy very much under the spell of Schopenhauer, who had thought that the world was an utterly vile, ghastly place. But Nietzsche thought that the ancient Greeks had found a way of using the truth, that the basic nature of existence is awful, to in some sense make their culture more energetic through tragic art. So you need the truth to energize itself, but then you need the illusion that art also provides to prevent the energy from blowing you apart roughly.