I came to the conclusion that koinonia often refers to a precise set of practices within the early Christian communities, a special social arrangement — the very one described in Acts — that was integral to the new life in Christ. When, for instance, the Letter to the Hebrews instructs believers not to neglect koinonia, or the First Letter to Timothy exhorts them to become koinonikoi, this is no mere recommendation of personal generosity, but an invocation of a very specific form of communal life.

As best we can tell, local churches in the Roman world of the apostolic age were essentially small communes, self-sustaining but also able to share resources with one another when need dictated. This delicate web of communes constituted a kind of counter-empire within the empire, one founded upon charity rather than force — or, better, a kingdom not of this world but present within the world nonetheless, encompassing a radically different understanding of society and property.

It was all much easier, no doubt — this nonchalance toward private possessions — for those first generations of Christians. They tended to see themselves as transient tenants of a rapidly vanishing world, refugees passing lightly through a history not their own. But as the initial elation and expectations of the Gospel faded and the settled habits of life in this depressingly durable world emerged anew, the distinctive practices of the earliest Christians gave way to the common practices of the established order.

Even then, however, the transition was not quite as abrupt as one might imagine. Well into the second century, the pagan satirist Lucian of Samosata reported that Christians viewed possessions with contempt and owned all property communally. And the Christian writers of Lucian’s day largely confirm that picture: Justin Martyr, Tertullian and the anonymous treatise known as the Didache all claim that Christians must own everything in common, renounce private property and give their wealth to the poor. Even Clement of Alexandria, the first significant theologian to argue that the wealthy could be saved if they cultivated “spiritual poverty,” still insisted that ideally all goods should be held in common.

As late as the fourth and fifth centuries, bishops and theologians as eminent as Basil the Great, Gregory of Nyssa, Ambrose of Milan, Augustine and Cyril of Alexandria felt free to denounce private wealth as a form of theft and stored riches as plunder seized from the poor. The great John Chrysostom frequently issued pronouncements on wealth and poverty that make Karl Marx and Mikhail Bakunin sound like timid conservatives. According to him, there is but one human estate, belonging to all, and those who keep any more of it for themselves than barest necessity dictates are brigands and apostates from the true Christian enterprise of charity. And he said much of this while installed as Archbishop of Constantinople.

That such language could still be heard at the heart of imperial Christendom, however, suggests that it had by then lost much of its force. It could be tolerated to a degree, but only as a bracing hyperbole, appropriate to an accepted religious grammar — an idiom, that is, rather than an imperative. Christianity was ceasing to be the apocalyptic annunciation of something unprecedented and becoming just the established devotional system of its culture, offering all the consolations and reassurances that one demands of religious institutions. As time went on, the original provocation of the early church would occasionally erupt in ephemeral “purist” movements — Spiritual Franciscans, Russian non-possessors, Catholic Worker houses — but in general, Christian adherence had become chiefly just a religion, a support for life in this world rather than a radically different model of how to live.

That was unavoidable. No society as a whole will ever found itself upon the rejection of society’s chief mechanism: property. And all great religions achieve historical success by gradually moderating their most extreme demands. So it is not possible to extract a simple moral from the early church’s radicalism.

But for those of us for whom the New Testament is not merely a record of the past but a challenge to the present, it is occasionally worth asking ourselves whether the distance separating the Christianity of the apostolic age from the far more comfortable Christianities of later centuries — and especially those of the developed world today — is more than one merely of time and circumstance.