It is a momentous venture to attempt to frame an hypothesis of the universe. But if we reflect upon the meaning of life, we are forced to make such an effort. The only way we can escape the responsibility is to be guilty of the great refusal—the refusal to think. If we frame an hypothesis, it should be such as to assign the proper significance to all the facts of human experience—not merely the physical facts, but the biological and mental as well; not merely our scientific interests, but our æsthetic, ethical, and religious interests as well. And it should do so in the simplest possible way. It would be futile and impossible to examine all possible solutions. Henri Poincaré proved long ago that if there is one explanation of a class of phenomena, there are an infinite number of explanations.