“A principal fruit of friendship,” Francis Bacon wrote in his timeless meditation on the subject, “is the ease and discharge of the fulness and swellings of the heart, which passions of all kinds do cause and induce.” For Thoreau, friendship was one of life’s great rewards. But in today’s cultural landscape of muddled relationships scattered across various platforms for connecting, amidst constant debates about whether our Facebook “friendships” are making us more or less happy, it pays to consider what friendship actually is. That’s precisely what CUNY philosophy professor Massimo Pigliucci explores in Answers for Aristotle: How Science and Philosophy Can Lead Us to A More Meaningful Life (public library), which also gave us this provocative read on the science of what we call “intuition.”

Philosophers and cognitive scientists agree that friendship is an essential ingredient of human happiness. But beyond the dry academic definitions — like, say, “voluntary interdependence between two persons over time, which is intended to facilitate socio-emotional goals of the participants, and may involve varying types and degrees of companionship, intimacy, affection and mutual assistance” — lies a body of compelling research that sheds light on how, precisely, friendship augments happiness. Pigliucci writes:

Happiness is influenced, as one might expect, by all of the “big five” personality traits: agreeableness, conscientiousness, extraversion, neuroticism, and openness. … As research conducted by Meliksah Demir and Lesley Weitekamp also clearly shows, however, friendship augments happiness above and beyond the basic effect of personality.

The way friendship enhances well-being, it turns out, has nothing to do with quantity and everything to do with quality — researchers confirm that it isn’t the number of friends (or, in the case of Facebook, “friends”) we have, but the nature of those relationships:

In particular, what makes for a good happiness-enhancing friendship is the degree of companionship (when you do things together with your friends) and of self-validation (when your friends reassure you that you are a good, worthy individual).

This is where Aristotle comes in: He recognized three types of love — agape, eros, and philia — which endure as an insightful model for illuminating the nature of our relationships. Pigliucci describes the taxonomy:

Agape is a broad kind of love, the kind that religious people feel that God has for us, or that a secular person may have for humanity at large. Eros, naturally, is more concerned with the type of love we have for sexual partners, though the Greeks meant it more broadly than we do. Philia is the type of love that concerns us here because it includes the sort of feelings we have for friends, family, and even business partners.

But this poses the obvious question of what separates love, or eros (itself a complex phenomenon nearly impossible to define, despite history’s ample attempts) from friendship, or philia — a conundrum young E. B. White and James Thurber famously considered and Sartre ultimately failed at resolving. Pigliucci explains:

The obvious answer is that typically (though certainly not necessarily) you have sex with your eros partner but not with your philia friends. More subtly, however, philosophers have pointed out that love is an evaluative attitude, while friendship is a relational one. It makes perfect sense that you could be in love with someone who doesn’t reciprocate your feeling, but it is incoherent to say that one has a nonreciprocal friendship.

Aristotle further classified friendships into three distinct categories: of pleasure, of utility, and of virtue:

In friendships of pleasure, you and another person are friends because of the direct pleasure your friendship brings — for instance, you like and befriend people who are good conversationalists, or with whom you can go to concerts, and so on. Friendships of utility are those in which you gain a tangible benefit, either economic or political, from the relationship. Exploitation of other people is not necessarily implied by the idea of utility friendships — first, because the advantage can be reciprocal, and second, because a business or political relation doesn’t preclude having genuine feelings of affection for each other. For Aristotle, however, the highest kind of friendship was one of virtue: you are friends with someone because of the kind of person he is, that is, because of his virtues (understood in the ancient Greek sense of virtue ethics [and] not in the much more narrow modern sense, which is largely derived from the influence of Christianity.)

But what it really boils down to is that friendship affords us a more dimensional way of looking at ourselves and at the world, thus enhancing our understanding of the meaning of life. Once again, Pigliucci takes us back to Aristotle:

Aristotle’s opinion was that friends hold a mirror up to each other; through that mirror they can see each other in ways that would not otherwise be accessible to them, and it is this (reciprocal) mirroring that helps them improve themselves as persons. Friends, then, share a similar concept of eudaimonia [Greek for “having a good demon,” often translated as “happiness”] and help each other achieve it. So it is not just that friends are instrumentally good because they enrich our lives, but that they are an integral part of what it means to live the good life, according to Aristotle and other ancient Greek philosophers (like Epicurus). Of course, another reason to value the idea of friendship is its social dimension. In the words of philosopher Elizabeth Telfer, friendship provides “a degree and kind of consideration for others’ welfare which cannot exist outside

Answers for Aristotle is excellent in its entirety. Complement it with some heartening famous friendships, like those between Isaac Asimov and Carl Sagan, Ernest Hemingway and F. Scott Fitzgerald, Julia Child and Avis DeVoto, Ursula Nordstrom and Maurice Sendak, and Arthur Conan Doyle and Harry Houdini.