What's bigger than a kazillion?

David Foster Wallace provides an entertaining tour of the mind-blowingly big numbers -- and establishes that some infinities are larger than others.

By Polly Shulman

Nov 12, 2003 | The greatest thrill I remember from my girlhood -- better than my first kiss, first airplane flight, first taste of mango, first circuit around the ice rink without clinging to a grown-up's sleeve -- was the heart-lifting moment when I first understood Georg Cantor's Diagonal Proof of the nondenumerability of the real numbers. This proof, the Mona Lisa of set theory (to my mind, the most satisfying branch of mathematics), changed the way mathematicians thought about infinity.

If you've ever thought much about numbers or talked with a preschooler learning to count, you've probably encountered some of the questions that led to Cantor's discovery a century ago. How many natural numbers are there? (Naturals are just the numbers we count with: 1, 2, 3, 4 and so on up forever.) And what about the even naturals: 2, 4, 6, 8 and so on? Infinitely many in both cases, right? OK, but are there more naturals than evens? Clearly every even natural number is a natural number, but there are plenty of naturals that aren't even -- namely the odds: 3, 5, 7, 9 and so on. Does that mean that the set of naturals is bigger than the set of even naturals?

What about the positive rational numbers -- fractions like 1/2, 17/23, 15/3? Are there more of those than the naturals? After all, the rationals include the naturals, since any natural number can be written as a fraction in lots of different ways (for example, 2 is 2/1, 4/2, 6/3 and so on). And what about the real numbers, which include the integers and the rationals, but also weird numbers like pi and the square root of 2, which can't be written as fractions -- are there more of those? Are there more points on a circle than there are seconds in eternity? How would you even begin to think about answering such questions?

Using reasoning that I've always thought of as his Squiggly Argument, Cantor proved that despite all the apparently extra fractions, there are just as many natural numbers as there are rational numbers. But don't jump to the conclusion that all infinities are the same size -- the gorgeous Diagonal Proof shows that there are more real numbers than naturals. A lot more -- infinitely many more, mind-bogglingly many more. And Cantor used the same method of argument to prove that there are not just two sizes of infinity, but mind-bogglingly infinitely many. His work on these infinitely large numbers, called cardinals and ordinals, raised questions that ultimately shook math to its foundations.

Yet Cantor's diagonal argument, in its essence, is so beautifully simple that even someone who hasn't yet entirely mastered trigonometry can understand it. I know, because I did, and so can you, whoever you are. I've often wanted to share the thrill with my intelligent but mathematically innocent friends and family -- English teachers, textile designers, photo editors, Internet journalists, soccer moms, wedding guests -- and I've succeeded, too, whenever I can get them to stay put. Being stuck in an elevator together helps. But elevators don't stall that often, so I was delighted to learn that the gloriously articulate novelist and essayist David Foster Wallace had written a history of infinity, with Cantor's Diagonal Proof as its climax. Now at last, I thought, I'll be able to spread the bliss without being treated like the Ancient Mariner.

Well, not really. "Everything and More: A Compact History of Infinity," though bristling with felicities, isn't for the mathematically timid. (Wallace doesn't use the word "infinity," but rather the sideways-8 symbol for it, which cannot be replicated in ASCII code.) In fact, it's hard to figure out just who the book is for. I relished Wallace's passionately erudite tone and the many exciting mathematical moments he helped me revisit, but there was nothing in "Everything" that I hadn't learned as an undergraduate math major. On the other hand, readers who haven't taken at least two semesters of calculus will probably have a hard time keeping up, despite Wallace's many protestations to the contrary. If you enjoyed math but quit after calculus because you didn't have room in your schedule; if you've forgotten quite a bit over the past few decades and want a stylish reminder; if you regret having focused on the discipline's real-world applications and wish you'd paid more attention to its philosophical issues; or if you're the captain of your middle school math team and have begun working through your big sister's calculus book because you're bored, then you'll love this book. Everyone else, try it anyway and prove me wrong. (Go ahead -- this elevator isn't going anywhere.)

Next Page: Wallace's appetite for detail is inspiring -- but enough with the partial differential equations!

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