In this weekend’s Wall Street Journal, I review A.C. Grayling’s Friendship. It’s a good book (despite its strained critique of the Christian of view friendship) and a timely reminder that possessing a few good friends is one of the touchstones of the “good life.” If you have too many friends, you are, according to Plutarch, “impressionable . . . pliant, and changeable” with an overly exuberant love of novelty. Have none, Francis Bacon writes, and you are “a wild beast.”

This holiday season I received Frédéric Lenoir’s Du bonheur (Of Happiness) from my in-laws. He makes a similar point regarding the importance of friendship, though he exaggerates the similarity necessary for people to bond and makes a somewhat odd remark regarding reciprocity. There is, he writes (roughly translated),

no true happiness without friendship. Aristotle does not distinguish between conjugal love and friendship. For him, they are the same emotion. Both require identity and reciprocity, which, in turn, unites spouses as it unites friends and results in their happiness. Identity because we recognize first in a friend “another self” with whom we share the same aspirations, tastes and interests–the same values and, eventually, the same life projects. We are happy to have found a being with whom we feel in communion on the essentials…Reciprocity because in order for love to flourish it must be shared. We can only be unhappy to love someone who does not love us in return.

Of course, having something important in common with someone else is necessary to develop a bond, but do I really need to share the “same life projects” with them to be friends? I’m not so sure. And while, it’s true that my happiness is surely diminished when I love someone who does not love me in return, I think it is a stretch to say that I can “only be unhappy” in this situation. Think of a parent who loves an indifferent child or even the companionship we have with our pets (which is not the same as human friendship, but it does share some of its qualities).

Human friendship is essential for happiness and for living a fully human life, but it is also wonderfully mysterious and cannot be unlocked by the keys of identity and reciprocity alone. This is why Lenoir adds a third element: “alterity”–that which “touches us in another person [and which is] his radical difference…that which is unique in him…We take pleasure in his singularity and his freedom.” Why would we love the singularity, the individuality, of someone else? A related question is why do we take pleasure in the being of other animals, the shape of a particular hill, the flow of a particular river, the way the sun sparkles off the snow?

What’s for sure is that this cannot be the result, as the social Darwinian would have it, of the survival value of reciprocity or our need for food and water alone. It requires, it seems to me, a spiritual answer.