Edwin Friedman ( A Failure of Nerve: Leadership in the Age of the Quick Fix ) notes that the intensity of an adulterous relationship arises from the way it creates an emotional triangle. The attraction is not the sex so much as the secrecy, which “creates an intense emotional bond by triangulating out the other partner.” The sense of aliveness that adulterers claim to experience in their adultery is a result of this secretive intensity.

He notes that “the way [the excluded partner] responds to the relationship of the other two . . . stabilizes or destabilizes the extramarital relationship. The relationship of B and C will take on a different tone if A mischievously encourages the affair than if A adopts a pouting, hurt, and suspicious attitude. Indeed, there may be no better proof that triangles are essentially an emotional process than the ways in which the intensity of B’s and C’s extramarital relationship is governed by the way A responds to it.”

Mutual hatreds can have a similar effect. B and C cultivate a common dislike for A, and this gives the relationship between B and C stability; “A, the third party (often unseen), [becomes] an inherent part of the connection of the other two.”