The connection between the face and ethical behavior is one of the exceedingly rare instances in which French phenomenology and contemporary neuroscience coincide in their conclusions. A 2009 study by Marco Iacoboni, a neuroscientist at the Ahmanson-Lovelace Brain Mapping Center at the University of California, Los Angeles, explained the connection: “Through imitation and mimicry, we are able to feel what other people feel. By being able to feel what other people feel, we are also able to respond compassionately to other people’s emotional states.” The face is the key to the sense of intersubjectivity, linking mimicry and empathy through mirror neurons — the brain mechanism that creates imitation even in nonhuman primates.

The connection goes the other way, too. Inability to see a face is, in the most direct way, inability to recognize shared humanity with another. In a metastudy of antisocial populations, the inability to sense the emotions on other people’s faces was a key correlation. There is “a consistent, robust link between antisocial behavior and impaired recognition of fearful facial affect. Relative to comparison groups, antisocial populations showed significant impairments in recognizing fearful, sad and surprised expressions.” A recent study in the Journal of Vision showed that babies between the ages of 4 months and 6 months recognized human faces at the same level as grown adults, an ability which they did not possess for other objects.

Without a face, the self can form only with the rejection of all otherness, with a generalized, all-purpose contempt — a contempt that is so vacuous because it is so vague, and so ferocious because it is so vacuous. A world stripped of faces is a world stripped, not merely of ethics, but of the biological and cultural foundations of ethics.

For the great existentialist Martin Heidegger, the spirit of homelessness defined the 20th century, a disconnected drifting in a world of groundless artificiality. The spirit of facelessness is coming to define the 21st. Facelessness is not a trend; it is a social phase we are entering that we have not yet figured out how to navigate.

As exchange and communication come at a remove, the flight back to the face takes on new urgency. Google recently reported that on Android alone, which has more than a billion active users, people take 93 million selfies a day. The selfie has become not a single act but a continuous process of self-portraiture. On the phones that are so much of our lives, no individual self-image is adequate; instead a rapid progression of self-images mimics the changeability and the variety of real human presence.

Emojis are an explicit attempt to replicate the emotional context that facial expression provides. Intriguingly, emojis express emotion, often negative emotions, but you cannot troll with them. You cannot send a message of faceless contempt with icons of faces. The mere desire to imitate a face humanizes.

But all these attempts to provide a digital face run counter to the main current of our era’s essential facelessness. The volume of digital threats appears to be too large for police forces to adequately deal with. But cases of trolls’ following through on their online threat of murder and rape are extremely rare. The closest most trolling comes to actual violence is “swatting,” or sending ambulances or SWAT teams to an enemy’s house. Again, neither victim nor perpetrator sees the other.