“Rules?" said Roark. "Here are my rules: what can be done with one substance must never be done with another. No two materials are alike. No two sites on earth are alike. No two buildings have the same purpose. The purpose, the site, the material determine the shape. Nothing can be reasonable or beautiful unless it's made by one central idea, and the idea sets every detail. A building is alive, like a man. Its integrity is to follow its own truth, its one single theme, and to serve its own single purpose. A man doesn't borrow pieces of his body. A building doesn't borrow hunks of its soul. Its maker gives it the soul and every wall, window and stairway to express it.”