IN 1988, Stephen Hawking, a British cosmologist, ended his best-selling book, “A Brief History of Time”, on a cliff hanger. If we find a physical theory that explains everything, he wrote—suggesting that this happy day was not too far off—“then we would know the mind of God.” But the professor didn’t mean it literally. God played no part in the book, which was renowned for being bought by everyone and understood by few. Twenty-two years later, Professor Hawking tells a similar story, joined this time by Leonard Mlodinow, a physicist and writer at the California Institute of Technology.

In their “The Grand Design”, the authors discuss “M-theory”, a composite of various versions of cosmological “string” theory that was developed in the mid-1990s, and announce that, if it is confirmed by observation, “we will have found the grand design.” Yet this is another tease. Despite much talk of the universe appearing to be “fine-tuned” for human existence, the authors do not in fact think that it was in any sense designed. And once more we are told that we are on the brink of understanding everything.

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The authors rather fancy themselves as philosophers, though they would presumably balk at the description, since they confidently assert on their first page that “philosophy is dead.” It is, allegedly, now the exclusive right of scientists to answer the three fundamental why-questions with which the authors purport to deal in their book. Why is there something rather than nothing? Why do we exist? And why this particular set of laws and not some other? . . . It soon becomes evident that Professor Hawking and Mr Mlodinow regard a philosophical problem as something you knock off over a quick cup of tea after you have run out of Sudoku puzzles.

. . . The authors also assert that the world’s past did not unfold of its own accord, but that “we create history by our observation, rather than history creating us.” They say that these surprising ideas have passed every experimental test to which they have been put, but that is misleading in a way that is unfortunately typical of the authors. It is the bare bones of quantum mechanics that have proved to be consistent with what is presently known of the subatomic world. The authors’ interpretations and extrapolations of it have not been subjected to any decisive tests, and it is not clear that they ever could be.