"The spin of a coin depends on chance. So do many of the things that take place in our minds: the precise moment of time when a new idea forms itself in a man's brain, for instance. But chance is a concept all too readily overworked. When at a loss to understand something, we are only too often tempted to suppose that our ignorance lies in a failure to trace some random quirk. And nowhere is this done more easily than in astronomy. Yet I think there are few studies in which chance is less important at root than it is in astronomy. The great stage where the Universe acts out its play is one on which the twin roles of coincidence and chance have scarcely any entry. From the vast expanding system of galaxies down to the humblest planet, and to the creatures that may live on it, there seems to be a strongly forged chain of cause and effect. Accidents there must be sometimes, but they matter not a jot to the march of the larger events.
The main theme of the present book lies not so much in any particular astronomical topic as in an attempt to write coincidence and chance out of the play. The first and last chapters have nothing factual in common, but they are linked by this underlying aim."