Sex and its combinations and permutations apart, two of Updike's commanding, long-standing intereststheology and various kinds of sciencecome together to form the matrix of his new novel. The conflicting ideas are as ancient as time: reason versus faith; science versus religion; belief versus any of the forms of unbelief. The contestants representing the fundamental opposition are the narrator, Roger Lambert, 52, a former minister, now a professor of divinity at a New England university, theologically a (Karl) "Barthian all the way" with a civilized tolerance for heretics and the steadfast conviction that God must be taken on faith; and Dale Kohler, 28, a computer scientist fixed in the belief that at the base of all science "God is showing through," now working on a definitive demonstration by computer technology of God's existence. That would keep anyone busy, but Dale finds a few hours a week for an affair with Roger's angry, unhappy wife, and Roger's version of belief does not prevent him from having a brief fling with his half-sister's daughter, herself an unmarried mother. For all Updike's finesse and dexterity in the deployment of ideas, there is more arcane computerology here than readers, including his most devoted, can digest by force-feeding, and probably more theology as well. Most readers will also think the characters contrived, mouthpieces for the perspectives they espouse.