From the exhibition, “Marina Abramovic, The Artist is Present,” at the Museum of Modern Art, New York, 2010. Credit Ruth Fremson/The New York Times

Philosophers and theologians in the Christian tradition have regarded human beings as distinguished from the other animals by the presence within them of a divine spark. This inner source of illumination, the soul, can never be grasped from outside, and is in some way detached from the natural order, maybe taking wing for some supernatural place when the body collapses and dies.

Recent advances in genetics, neuroscience and evolutionary psychology have all but killed off that idea. But they have raised the question of what to put in its place. For quite clearly, although we are animals, bound in the web of causality that joins us to the zoosphere, we are not just animals.

There is something in the human condition that suggests the need for special treatment. Almost all people believe that it is a crime to kill an innocent human, but not to kill an innocent tapeworm. And almost all people regard tapeworms as incapable of innocence in any case — not because they are always guilty, but because the distinction between innocent and guilty does not apply to them. They are the wrong kind of thing.

We, however, are the right kind of thing. So what kind is that? Do any other beings, animal or otherwise, belong to it? And what follows? These questions lie at the center of philosophical inquiry today, as they have since the ancient Greeks. In a thousand ways we distinguish people from the rest of nature, and build our life accordingly. We believe that people have rights, that they are sovereign over their lives, and that those who live by enslaving or abusing others are denying their own humanity. Surely there is a foundation for those beliefs, just as there is a foundation for all the moral, legal, artistic and spiritual traditions that take the distinctiveness of human life as their starting point.

If, as many people believe, there is a God, and that God made us in his own image, then of course we are distinct from nature, just as He is. But talk of God’s image is a metaphor for the very fact that we need to explain, namely that we treat the human being as a thing apart, a thing protected by a sacred aura — in short, not a thing at all, but a person.

Much 20th-century philosophy is addressed to the question of how to define this fact in secular terms, without drawing on religious ideas. When Sartre and Merleau-Ponty write of “le regard” — the look — and Emmanuel Levinas of the face, they are describing the way in which human beings stand out from their surroundings and address one another with absolute demands of which no mere thing could be an object. Wittgenstein makes a similar point by describing the face as the soul of the body, as does Elizabeth Anscombe in describing the mark of intentional action as the applicability of a certain sense of the question “Why?”

Human beings live in mutual accountability, each answerable to the other and each the object of judgment. The eyes of others address us with an unavoidable question, the question “why?” On this fact is built the edifice of rights and duties. And this, in the end, is what our freedom consists in — the responsibility to account for what we do.

Evolutionary psychologists tell another story. Morality, they argue, is an adaptation. If organisms compete for resources, then a strategy of cooperation will be more successful in the long run than a strategy of pure selfishness. Hence cooperative features of an organism will be selected over time. And all that is special in the human condition can be understood in this way — as the outcome of a long process of adaptation that has conferred on us the insuperable advantage of morality, whereby we can resolve our conflicts without fighting and adjust to the demands that assail us from every side.

The astonishing moral equipment of the human being — including rights and duties, personal obligations, justice, resentment, judgment, forgiveness — is the deposit left by millenniums of conflict. Morality is like a field of flowers beneath which the corpses are piled in a thousand layers. It is an evolved mechanism whereby the human organism proceeds through life sustained on every side by bonds of mutual interest.

I am fairly confident that the picture painted by the evolutionary psychologists is true. But I am also confident that it is not the whole truth, and that it leaves out of account precisely the most important thing, which is the human subject. We human beings do not see one another as animals see one another, as fellow members of a species. We relate to one another not as objects but as subjects, as creatures who address one another “I” to “you” — a point made central to the human condition by Martin Buber, in his celebrated mystical meditation “I and Thou.”

We understand ourselves in the first person, and because of this we address our remarks, actions and emotions not to the bodies of other people but to the words and looks that originate on the subjective horizon where they alone can stand.

This mysterious fact is reflected at every level in our language, and is at the root of many paradoxes. When I talk about myself in the first person, I utter propositions that I assert on no basis and about which, in a vast number of cases, I cannot be wrong. But I can be wholly mistaken about this human being who is doing the speaking. So how can I be sure that I am talking about that very human being? How do I know, for example, that I am Roger Scruton and not David Cameron suffering from delusions of grandeur?

To cut the story short: By speaking in the first person we can make statements about ourselves, answer questions, and engage in reasoning and advice in ways that bypass all the normal methods of discovery. As a result, we can participate in dialogues founded on the assurance that, when you and I both speak sincerely, what we say is trustworthy: We are “speaking our minds.” This is the heart of the I-You encounter.

Hence as persons we inhabit a life-world that is not reducible to the world of nature, any more than the life in a painting is reducible to the lines and pigments from which it is composed. If that is true, then there is something left for philosophy to do, by way of making sense of the human condition. Philosophy has the task of describing the world in which we live — not the world as science describes it, but the world as it is represented in our mutual dealings, a world organized by language, in which we meet one another I to I.