The facts are indispensable; they are not sufficient. To solve a problem it is necessary to think. It is necessary to think even to decide what facts to collect. Even the experimental scientist cannot avoid being a liberal artist, and the best of them, as the great books show are men of imagination and of theory as well as patient observers of particular facts. ... critics have themselves frequently misunderstood the scientific method and have confused it with the aimless accumulation of facts.