Other people have treated it as a real question, the kind that might have an answer. And some think they have actually found answers, though these tend to be so different that one can hardly believe they started with the same question.

In “Why Does the World Exist?,” Jim Holt, an elegant and witty writer comfortably at home in the problem’s weird interzone between philosophy and scientific cosmology, sets out in search of such answers. He takes inspiration from readings of Heidegger and Sartre, and from something Martin Amis once said in a television interview: “We’re at least five Einsteins away from answering that question.” Holt, a frequent contributor to the Book Review, speculates that some of these Einsteins might be at work already. “If I could find one, or maybe two or three or even four of them, and then sort of arrange them in the right order,” he says amiably, “well, that would be an excellent quest.” In fact, he finds eight thinkers worthy of a chapter each, as well as some bit-players like a Zen Buddhist who answers the question by attempting to bop Holt on the head, koan style. The Zen angle ends there, and Holt is similarly unimpressed by the approaches of monotheistic religion.

So he travels to Paris, London, Oxford (several times), Pittsburgh and Austin, Tex., to meet the philosophers and cosmologists David Deutsch, Adolf Grünbaum, John Leslie, Derek Parfit, Roger Penrose, Richard Swinburne and Steven Weinberg. He also has a discussion with the philosophically inclined novelist John Updike. As he moves from one to the other, Holt learns of ever more extraordinary solutions, some almost mystical, yet rooted in solid reasoning.

His first interlocutor, the philosopher Adolf Grünbaum, throws down a challenge: Why be astonished at being at all? To marvel at existence is to assume that nothingness is somehow more natural, more restful. But why? The ancients started with matter, not the void; perhaps nothingness is stranger than being.

Holt’s other conversations are with people who do marvel at being, but they also confirm Grünbaum’s point about the puzzling nature of nothingness. It is all very well to say the universe started with a Big Bang, but how? Did it burst out like “a party girl jumping out of a cake,” as Fred Hoyle put it? But how can one even speak of cakes, or of “bursting out,” when there is no pre-Bang time or space from which to burst? As Holt says, we tend to think of the start of the universe by analogy with a concert, where we sit fiddling with our programs until the music begins. But there is no tuning-up, no fiddling. It’s hard to visualize nothingness, though Holt quotes a beautiful definition by the physicist Alex Vilenkin: “a closed spherical spacetime of zero radius.” Try jumping out of that.