"It doesn't negate a God, though," says Hamilton, who points out that there are Buddhist Jews, Catholics and Mormons. Earlier, sitting in their kitchen, she and Zimmerman had been talking about whether the fact that they met was accidental or was something more akin to destiny. "There's something intelligent at work" in the universe, Hamilton had asserted. "I don't know if I would say it's 'intelligent,' " Zimmerman countered. "OK, the universe isn't intelligent but you are?" Hamilton chided. It was a good-natured exchange, but it's also clear that husband and wife don't always see eye to eye on this God thing.

The experiential nature of Zen — the insights that come only through "sitting" — is similar to the mysticism of Christianity and Sufism, Zimmerman says; and it's why it's so hard to explain without using metaphor and analogy. Trying to explain Zen, he says, is akin to asking someone to describe the taste of water.

Still, when pressed, he tries to explain. Sit, morning after morning, with your own mind, just watching your mind, he says, and eventually "the more you look at this idea of self, you realize you can't put your finger on it." The self is just an intellectual construct, he says, invented by a mind that has trouble separating the self from everything else that is experienced through the senses.

Accessing this sense of oneness — what Buddha called enlightenment, what other religious traditions might call God — has always been the challenge, notes Hamilton. Some people use prayer or fasting or other ritual. And some people use meditation.

Lose the sense of self and you become more compassionate, says Hamilton. "So compassion is also a fruition of sitting." And so is an ability to see a problem from different perspectives. That's why meditation and mediation are, in a sense, the same activity, she says. "They involve taking what is two and discovering what is one."

A few days later, Zimmerman, Hamilton and Willie drive over to the Zen Center for a class taught by Genpo Roshi. In the upstairs meditation room they join 20 or so others, who begin the session in silent sitting, and then listen to Roshi discuss the finer points of Zen.

Our dualistic minds can't understand Buddha's insight that we are all Buddha, Roshi says. Then he launches into a discussion of "the unsurpassable mantra that clears all pain."

Willie fidgets on his cushion but listens as Roshi speaks and people ask questions. Then he raises his hand with a comment of his own. "Some Buddhists like to think a lot," he says. "And some Buddhists do what they like to do. And some Buddhists have dog weddings." Willie is hoping that his dog Ali can marry Roshi's dog Tibby.