In the first portion of the book (chaps. 1–6), Krauss guides the reader through a whirlwind tour of the latest advances in cosmology and astrophysics, organized around the overarching theme that science can provide us with genuine insight about the universe by leading us down paths that religion and philosophy dare not trod. Starting with the groundbreaking discovery that our universe had a beginning in the finite and measurable past (due in large part to the Jesuit priest Georges Lemaître) known as the “Big Bang” (21), Krauss emphasizes how further scientific research has prompted two key realizations. First, the universe is composed not simply of visible matter, but also, and to a very large degree, “dark matter” (34); and second, our best mapping of the background radiation of the universe, enables us to conclude that the universe is not curved, but is flat in the sense that light travels through it in straight lines (54). Krauss notes however that even with the addition of dark matter, roughly 70 percent of the energy required for the universe to come out flat is simply missing (55). It is here that Krauss begins to move toward the puzzle how something might come from nothing, and describes in detail his startling proposal that the missing energy can be found residing not in matter, but in empty space itself (75). For what may seem for all intents and purposes like empty space is really a realm of quantum fluctuations able to give rise to energy from genuine “quantum nothingness” in what Krauss considers to be the quintessential example of a cosmic “free lunch” (98).
After introducing us to the intriguing possibility of how something can come from “nothing,” Krauss devotes the remainder of the book (chaps. 7–11) to applying this possibility to the problem of the origin of the universe itself. For Krauss, advances in science have now placed us in a better position to answer the question of why there is something rather than nothing. In fact, it helps us to understand that the significant question is not “why” but “how,” a question that we can answer through study of the natural world (144). For Krauss, the answer simply resides in the fact that “nothing” is not really nothing, but rather seemingly empty space endowed with energy from which “something” can genuinely arise (152). Further, Krauss argues that given the implications of quantum gravity, universes may very well appear spontaneously out of nothing even in the absence of space and time, which ultimately answers the question of how the universe came from nothing at all (171). This, Krauss concludes, is the scientific answer to the question of why there is something rather than nothing.
Krauss’s book, while engaging and stimulating in its prose, nevertheless is plagued by a conceptual identity crisis. As a work of popular science literature, A Universe From Nothing is a dazzling display of science writing at its very best, with Krauss deftly handing some highly technical and complex scientific ideas in ways that make them open and accessible to the non–specialist. Unfortunately, Krauss becomes less convincing when he shifts from describing the science behind astrophysics and cosmology to providing an answer to the philosophical question of why there is something rather than nothing. This difficulty stems from a severe misunderstanding of what the question means. The heart of Krauss’s proposal seems to be that while for centuries theologians and philosophers have labored under the mistaken assumption that empty space was nothing, science has now shown us that not only what seems to be “nothing” actually contains energy at the quantum level, but that the universe itself could have sprung from this nothingness.
However, what Krauss has simply done is equivocated the “nothing” which philosophers take to be the absolute absence of anything at all with a “nothing” that for Krauss is simply a particular description of quantum energy inhabiting empty space. The end result is that all Krauss has provided us with is a scientifically informed description of how something can come from something, which is not a particularly startling philosophical revelation. While Krauss does seem to acknowledge that he has not answered the puzzle of the origin of the universe in a way that is philosophically convincing, Krauss simply dismisses this fact and retorts that all this means is “nature may be cleverer than philosophers or theologians” (174). Unfortunately, this cavalier attitude towards any form of reasoning outside of the natural sciences characterizes much of Krauss’s book, which is peppered with thinly veiled invectives against philosophy and theology.