I have had friendship proposed to me a few times, usually resulting in a life-giving relationship. One proposal, however, was a failure, and perhaps a moral one on my part.

The tiny liberal arts college that I attended used to require its students to write a somewhat formidable thesis in our senior year. My graduating class was the one that, through systemic negligence and procrastination, drove the administration to make the project optional for future classes. But most of us at least attempted to muster a decent-looking manuscript, muscling past a crippling imposter syndrome while writing on topics so broad, unwieldy, and ambitious they would have given tenured faculty profound anxiety.

One of my classmates decided to write on friendship. Yet this particular classmate, ironically, had never quite found his clique in our close-knit community. At our college, we were mostly nerds of various species—quoting G.K. Chesterton, translating Virgil from the Latin, avidly attending Sacred Harp psalm sings at the local Unitarian church. But within this eggheaded biosphere, it seemed to me that our classmate hadn’t managed to find a home. I certainly never made an effort to reach out. I sat inconspicuously in the back row of every class; he was an eager front-row dweller. I wore JC Penney khakis and gingham shirts; he wore Brooks Brothers suits. With aspirations to fit in with the indie crowd, I listened to Sufjan Stevens’s Illinois and Death Cab’s Plans on repeat; I was ignorant (perhaps culpably so) of whether he enjoyed pop music at all. From my blinkered perspective—within our tiny, homogeneous, insular community—we inhabited very different worlds.

But after a mid-week lecture one day, he approached me and asked me to lunch. We had never hung out one-on-one, and rarely in groups. It seemed a strange request, but also impossible to turn down in the moment. So later that week he took me out to a local coffeeshop. Soon after sitting down, he asked me directly: Would I like to try being friends? And would I perhaps even talk with him about his ongoing thesis project?

What ought one to do in this situation? From my perspective as a not-quite-mature adult, he and I possessed very few common interests. We had never connected before, and he was not part of any of the social cliques of which I was a member, or of which I desired to become a member. There were no obvious prospects, I assumed, for a friendship that would outlast our final year in college. And yet here he was, proposing friendship, almost experimentally.

In my recollection, which is admittedly clouded by some remorse, I agreed to his proposal. But I never acted on it. I never reciprocated his lunch invitation, and I never read a word of his thesis. It wasn’t a term at the time, but I suppose I ghosted him, despite seeing him in class several times a week for the rest of the year.

When I teach on friendship now, I ask my students whether they think I was morally culpable for what I did—or did not do—in this situation. Most, strikingly, do not think so. Possibly motivated by a desire to assuage my guilt, or perhaps their own, they generally think that I was under no obligation to accept his offer of friendship. Friendship is not—and cannot be—universal, they tell me. Certainly, it would have been a wonderful thing if my classmate and I had had enough in common to sustain a meaningful friendship. But why feel guilty decades later about the fact that no such commonality existed?

One student, however, returned my question about culpability with a question of her own: Why didn’t my classmate and I share more in common? Underlying her question was the implication that I had made a series of choices that led me to the place where I could not imagine having a long-standing relationship with him. I had chosen to associate with certain cliques, hadn’t I? I had chosen to cultivate certain interests and passions that were incompatible with my classmate’s, hadn’t I? Wasn’t I also responsible for my incuriosity about his own history and hobbies?

These questions suggest an interesting moral intuition: Perhaps our affinities are not written in stone. Perhaps the prospect of a friendship with someone is itself reason to develop—or at least endeavour to develop—some mutual interests. We happen upon specific friendships, yes, but should we also be intentional about cultivating the types of soil in which those friendships may grow? And by implication, aren’t we culpable when our friends all look, act, dress, and vote like we do?

I once posed this question to one of my senior colleagues, someone who has written—to my mind—some of the most penetrating theological reflections on friendship in recent decades. Without hesitating, he responded drolly that I should find a therapist, not a moral philosopher, to process whatever residual guilt I had over the narrowness of my friendships. Why feel guilt over the simple fact that friendship consists in the exclusivity of alikeness?

Perhaps my colleague and most of my students are right. Adding to their number, most premodern philosophers evince little anxiety about the homogeneous exclusivity of friendship. Aristotle could not imagine true friendship between a social superior and a social inferior, and many of his intellectual descendants applied this skepticism to relationships between men and women, old and young, rich and poor. In his classic book The Four Loves, even C.S. Lewis, a medievalist but not a medieval, professed that most men find the presence of women in their friend circles an intrusion.

Is natural attraction to sameness a problem? Or is it simply inextricable from friendship? Can we distinguish between its benign and vicious forms? Or is our moral anxiety about sameness misbegotten?

I suspect that most of us, including the premodern philosophers, would admit that some forms of affinity relationships are potentially harmful, at least on a larger scale. For instance, patriotism—the virtuous love of country—can easily drift into excess and even idolatrous nationalism and nativism.

These temptations are perennial in nature, and yet they have taken on additional urgency in recent years as some Christian thinkers have argued that it is simply natural for human beings to prefer homogeneous communities—not just in their personal lives but also in their churches and their nation-states. Love of “one’s own” is made the fundamental maxim for organizing society. Disturbingly, some have even defended a form of (ostensibly Christian) ethno-nationalism, suggesting that “no nation is composed of two or more ethnicities.”

It is the work of prudence to distinguish between legitimate desires, such as an appropriate love of one’s home and people, and their vicious semblances. And while—we might hope—a wise person will quickly discern the viciousness of those who long for a mono-ethnic theocracy, a more fundamental question remains: Should Christians be content with only affinity love? What obligations do we have beyond love of “one’s own”? What of those whom, on account of their values or identities, we would never consider even potential friends?

I believe this is the most important question for Christians working in public life for the common good. Practically speaking, what would it mean to love the unfamiliar, the strange, the objectionable, even the abhorrent?

Love of enemy—which is what we now find ourselves considering—is an impossible task. At least if we are honest with ourselves. Love of enemy is also perhaps the most distinctive Christian moral imperative. What would it look like if we made friends of enemies? What would it look like if we took on the burden of choosing to befriend those we take to be different from us? Indeed, what would it look like if we decided to cultivate interests, habits, and loves that align not only with our neighbour (a hard enough task) but even with our enemy?

The resulting imperatives seem hard but are even harder to escape: Choose to learn another’s customs. Choose to worship in unfamiliar spaces. Learn the life stories of those whose identities you consider alien and objectionable. And not least, accept the strange and unexpected offer of friendship when it is proposed. Perhaps I sound suspiciously like the therapist my senior colleague drolly dismissed. But I wonder whether the particular bundles of loves that constitute a human person are so fixed and resistant to the agency of grace—human or divine.

Love of enemy, by definition, is a non-reciprocal love. It is a love offered with hope—but no presumption—of return. So perhaps the moral therapy I am suggesting will yield no relational revelations, no socio-political breakthroughs. Even so, Christians might remember that we love because there is one who first loved us. The incarnational pattern is this: we who were enemies of God were brought into fellowship through the condescension of the transcendent Lord who took on all blemishes, hopes, fears, and trials that befit human flesh. That kind of loving sacrifice—whether on the cosmic, political, or personal scale—tends to have an effect.

This essay is adapted from “Choosing the Impossible Love” in the Center for Christianity and Public Life’s Journal of Ideas.