If we do discover a complete theory, it should in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all, philosophers, scientists, and just ordinary people, be able to take part in the discussion of the question of why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason — for then we would know the mind of God.

Last lines. Hawking later wrote: "In the proof stage I nearly cut the last sentence in the book... Had I done so, the sales might have been halved. - Black Holes and Baby Universes and Other Essays (1993)