03/18/2010 05:12 am ET Updated May 25, 2011

Why There Are Seven Dwarfs and Seven Deadly Sins

More than 835,000 books have the word "seven" in their title. I estimate that about half of them are currently in our apartment, largely because my spouse, the esteemed Jackie Leo, has been writing the definitive book "Seven,"and she refused to do that without a decent amount of room-filling research.

As I snake through the narrow paths in our home that do not yet have stacks of numerological books piled toward the ceiling, always threatening to tip over and extinguish one of our cats, I think back to the fateful day when Jackie decided on this project. It dawned on her that she and her friends have a lot of big cookbooks, but they generally use only about seven recipes from each. And they may have a closetful of clothes (sorry--closetful of fashion) but aside from special occasions they wear the same seven outfits over and over.

So Jackie concluded, and she has some academic work to support it, that the number seven acts as a kind of brain filter, limiting choices and cutting down lists we are reluctant to remember. It's the reason why we easily recall, for instance, the seven digits of a phone number, but not those infuriating extra numbers tacked onto the end of zip codes.

It's also the reason why sevens are everywhere--deadly sins, samurai, hills of Rome dwarfs, wonders of the world, sacraments, days of the week, ages of man, etc., etc. Once you start noticing, the sevens seem relentless. Seven Against Thebes, Seven Brides for Seven Brothers, 77 Sunset Strip. Jackie reminds us that the McDonalds Big Mac has seven ingredients, and that Paul Simon may sing about fifty easy to leave your lover, but the song lyrics list only seven. It got the point where I expected our car to stop automatically at every seven eleven. I was hoping that the number of Tiger Woods mistresses would top out at seven, but no, it rose to 14, which at least is a multiple of seven.

Seven appears in way more movie titles than any other number. On my own, I got interested in how the concept of a seventh son of the seventh son (or the seventh daughter of a seventh daughter) got to be so popular and mesmerizing. On the Internet you can find a debate as to whether the Irish or the Mohawk developed the idea (we can rule out Iron Maiden as a musical latecomer), but in fact it is found in the Bible and pops up around the world in a great many cultures as a healer or positive figure. One exception would be Romania, where the seventh of a seventh is expected to be a vampire. (Once again, Romania finds itself on the cutting edge of modern popular culture.) Of the seventh daughter of a seventh daughter, we know very little, except that her mother and grandmother must be very tired.

At a recent dinner party, Jackie decided to send some Zinfandel to the hostess. The name of the wine, coming from seven different California vineyards, was of course, the Seven Deadly Zins. At a party in Jackie's honor 7 and 7s were available (Seagrams and 7up) but no seven-layer cake--a relief to all. The real feature was a first-rate Napa Valley Cabernet, 7, donated by the generous owner of Vineyard 7 and 8. He is a Manhattan hedge fund specialist, Launny Steffens. We didn't know the man, but we know him now. He showed up at the party and seemed to have a very good time. See what a positive number 7 is?