"There are people in the world whose imagination is so vivid that when they have an idea it comes to them as an audible voice, sometimes uttered by a visible figure. Criminal lunatic asylums are occupied largely by murderers who have obeyed voices...But the seers of visions and the hearers of revelations are not always criminals. The inspirations and intuitions and unconsciously reasoned conclusions of genius sometimes assume similar illusions. Socrates, Luther, Swedenborg, Blake saw visions and heard voices just as Saint Francis and Saint Joan did. If Newton's imagination had been of the same vividly dramatic kind he might have seen the ghost of Pythagoras walk into the orchard and explain why the apples were falling. Such an illusion would have invalidated neither the theory of gravitation nor Newton's general sanity. What is more, the visionary method of making the discovery would not be a whit more miraculous than the normal method. The test of sanity is not the normality of the method but the reasonableness of the discovery."