Perhaps the most important lessons Stephen Hawking imparts to the general public in this book are (1) that the techniques of science can discover how the universe works without appealing to revealed knowledge or supernatural forces and (2) that science can solve the problems that plague humanity. Whereas people once explained the mysteries of life—storms, lightning, earthquakes, diseases—as the arbitrary decisions of gods, in the past few hundred years science has discovered natural explanations for nearly all of these phenomena. Hawking asserts that gods need not intervene in reality or even create it; the laws of physics dictate the beginning, middle, and end of the universe’s history. Regardless of whether a god exists, claims Hawking, such an entity wouldn’t meddle in our affairs. Instead, nature behaves in an orderly manner that, even at its extremes, humans can discern using the tools of science.

In recent decades, scientists have established two great pillars of physics: relativity theory, which sets the rules for the universe at large, and quantum mechanics, which defines the behavior of the microscopically small. These two monuments of the human intellect have brought a complete understanding of the workings of the cosmos almost within reach.