Mate Tectonics

The stranger who answered the door at my friend Kate's birthday party looked right at home. He was smiling. He was drinking beer. He was clutching a potholder. "Come on in." He gestured expansively toward Kate's living room. "I'm Jim. What can I get you to drink? We have beer and wine and ..."

As soon as the word "we" escaped his lips, I stopped wondering who he was. After all, I hadn't seen Kate in nearly a month, and a month, in dating years, is roughly equivalent to the entire Paleozoic Era. Seismic shifts can occur. Glaciers can melt. Couples can evolve -- or simply explode into being.

That, I later learned, was what had happened to Kate and Jim in the month since I'd seen her. They had met online, gone on three great dates, and -- as fast as you can say "big bang" -- had officially become a Couple. The evidence was everywhere, from the Right Guard in Kate's bathroom to the man-sized sweatshirt hanging on a doorknob. You could even hear the change: Kate gently reminding Jim to take his allergy medicine, Jim fumbling in the role of co-host, both of them speaking in the first-person plural.

They seemed happily, intensely, self-consciously coupled. And a month later, they broke up. "Jim," said Kate, when she called to announce the end of the Jim-ozoic Era, "really isn't who I thought he was."

If you are a single person seeking a life partner, or if such a person has your phone number, then the story of Kate and Jim may sound familiar. Theirs was a classic example of what a friend calls "radical intimacy": a tendency, common among the marriage-minded, to proceed directly from a second or third date to an idealized, yet temporary, domesticity. Couples in the throes of radical intimacy swap favorite books and CDs with abandon. They stock their kitchens with one another's favorite cereal. They spend every night together. They do all this within weeks, if not days, of a first meeting.

Given that sex usually enters the equation at roughly the speed of light, some might argue that radical intimacy is nothing more than promiscuity dressed up as a legitimate relationship. But ironically, my friends who date this way -- both male and female -- usually want nothing more than to escape the singles scene forever. They want all the good things being in a couple supposedly provides: love, stability, children, a reason to register at Crate & Barrel. They have clear ideas about the person they'd like to do these things with. So when they meet someone who seems, on the second or third date, to be "the one," they rush in, hearts first and toothbrushes outstretched.

The hitch, of course, is that no one is ever as good as the partner of your dreams, because the partner of your dreams is a product of your own marvelous imagination. But the desire to be in a couple can mask the differences between the person you'd like to be dating and the person you actually are dating -- at least for a while. After the one-month mark, some couples discover unacceptable differences between the fantasy and the reality, and, like Kate and Jim, they call it quits. Other couples have the same problems and ignore them, unwilling to admit, to themselves or the world, that their instincts were wrong. And still others, the lucky ones, discover that the person they've leapt into intimacy with is, indeed, the person they want to be intimate with.

Take my friends Polly and Sam. They like to say that, despite a year of marriage, they're still on their first date. Why? "Because since the first moment I saw her, we haven't been apart. I haven't been able to let her out of my sight," says Sam, 31. We all know couples like Polly and Sam. Some of us may even secretly loathe them.

But I think it's stories like theirs that keep radical intimacy in business, putting strange faces into familiar doorways and leaving behind a wake of abandoned toothbrushes. It's stories like theirs that makes daters like Kate risk their CDs, their sexual health, and their hearts in the hopes that next time -- big bang! -- they'll enter a romantic era mighty enough to withstand a second coming of the glaciers.

Or, at the very least, mighty enough to last till death does them part.

Alison Lobron teaches at Concord Academy. To respond, send e-mails to coupling@globe.com.