While goofing off on the Internet—and wondering what ever happened to Sunday strolls—I chanced across one of those Puppy Dog sales come-ons for an e-book. (Puppy Dog come-ons were invented or at least popularized by car salespeople who are forever begging you to take their shiny model home and drive it for the weekend, knowing full well that, like a puppy dog, once you’ve had it for a weekend, you are going to be tempted to keep it much longer, at least until you get Puppy Dogged yet again.) I have to admit that this author, Daniel Gilbert, a Harvard psychologist, had me hooked from the get-go with the first two paragraphs to his new book, Stumbling on Happiness.

You can see if your anti-Puppy Dog filter works any better than mine by reading these paragraphs for yourself:

O, that a man might know The end of this day’s business ere it come!—Shakespeare, Julius Caesar. Priests vow to remain celibate, physicians vow to do no harm, and letter carriers vow to swiftly complete their appointed rounds despite snow, sleet, and split infinitives. Few people realize that psychologists also take a vow, promising that at some point in their professional lives they will publish a book, a chapter, or at least an article that contains this sentence: “The human being is the only animal that . . .” We are allowed to finish the sentence any way we like, of course, but it has to start with those eight words. Most of us wait until relatively late in our careers to fulfill this solemn obligation because we know that successive generations of psychologists will ignore all the other words that we managed to pack into a lifetime of well-intentioned scholarship and remember us mainly for how we finished The Sentence. We also know that the worse we do, the better we will be remembered. For instance, those psychologists who finished The Sentence with “can use language” were particularly well remembered when chimpanzees were taught to communicate with hand signs. And when researchers discovered that chimps in the wild use sticks to extract tasty termites from their mounds (and to bash one another over the head now and then), the world suddenly remembered the full name and mailing address of every psychologist who had ever finished The Sentence with “uses tools.” So it is for good reason that most psychologists put off completing The Sentence for as long as they can, hoping that if they wait long enough, they just might die in time to avoid being publicly humiliated by a monkey.

I have never before written The Sentence, but I’d like to do so now, with you as my witness. The human being is the only animal that thinks about the future. Now, let me say up front that I’ve had cats, I’ve had dogs, I’ve had gerbils, mice, goldfish, and crabs (no, not that kind), and I do recognize that nonhuman animals often act as though they have the capacity to think about the future. But as bald men with cheap hairpieces always seem to forget, acting as though you have something and actually having it are not the same thing, and anyone who looks closely can tell the difference. For example, I live in an urban neighborhood, and every autumn the squirrels in my yard (which is approximately the size of two squirrels) act as though they know that they will be unable to eat later unless they bury some food now. My city has a relatively well-educated citizenry, but as far as anyone can tell its squirrels are not particularly distinguished. Rather, they have regular squirrel brains that run food-burying programs when the amount of sunlight that enters their regular squirrel eyes decreases by a critical amount. Shortened days trigger burying behavior with no intervening contemplation of tomorrow, and the squirrel that stashes a nut in my yard “knows” about the future in approximately the same way that a falling rock “knows” about the law of gravity—which is to say, not really. Until a chimp weeps at the thought of growing old alone, or smiles as it contemplates its summer vacation, or turns down a taffy apple because it already looks too fat in shorts, I will stand by my version of The Sentence. We think about the future in a way that no other animal can, does, or ever has, and this simple, ubiquitous, ordinary act is a defining feature of our humanity.

You can read a few more paragraphs of Dr. Gilbert’s work for free (in fact, you’ll have to read them to find out what he thinks the human brain’s greatest achievement is) and find order information here: Stumbling on Happiness