I often commute to Tokyo for work. There are many train lines in Japan, and in the capital, they weave and tangle like cat’s-cradle strings. Some evenings, on the long ride home, my train ends up running parallel for a few moments with some other train on some other track headed for some other destination. In that brief span of time, I can see the faces of passengers in the other train as it passes.

“Petals on a wet, black bough” is how the poet Ezra Pound described the faces he saw on the metro. The people I used to see in stilled zoetrope in temporarily neighboring trains were reading, talking, lost in thought, maybe staring out the window like I was. Their faces were like invitations; each a world of its own, each of their lives a story that I could guess at, a puzzle which I could try, in the space of a handful of seconds, to solve. The faces in those trains made me ache in a way. They came close and I wanted to know more about them. But then, in an instant, they were gone.

Recently, though, the faces I see on parallel trains are not invitations. Almost every one of them glows eerily, lit from below by a screen. The human face, normally a powerful moral fact, as the philosopher Emmanuel Levinas taught us, is rendered by smartphone absorption into a twisted mask. One feels strangely excluded, brushed aside, pushed into a background that the screen-gazer is trying to keep from intruding on his or her virtual experience somewhere online. His or her face is a kind of nowhere, a vacancy, an absence where, normally, the human person demands to be recognized as an Other with infinite dignity.

To put things a bit differently, the human face, ideally, is a kind of eros, a Platonic incompleteness that seeks an Other to recognize and to be recognized by. In Japanese, one way to say “eros” is iroppoi, which has connotations of “fetching” or “come-hither” but literally means “with a touch of color.” Colors are like faces, I think. Colors are mysteries. Nobody knows what they are or why they exist. Nobody can describe a color. One has to see the color to know what it is. Human faces, too, need to be seen to be understood, but even then there is no end to their mystery. We can get used to faces, but we can never, no matter how much we gaze, come close to knowing who, really, is the person who wears it, how deep is her dignity, how much she is loved by God. From the face of an elderly person to the face of an infant in the womb peering back at us through ultrasound, the human person is “colored,” that is, each human being is a mystery that we can experience but never truly know. A face, like a color, is both a fact and an invitation. Puzzle over either one as long as you like. Unlike a color, though, a face is a person made visible, a world, and a portal to entering that world, a story and an invitation all at once.

I was back on the train today, coming home from work in Tokyo. We were still in the subway section of the train line, so no parallel cars were in sight. But suddenly, at one station, two people got on the car and stood right in front of me, already engaged in intense conversation. Their talk was in sign language. Their hands made flowing, rapid-fire shapes and symbols in the air in front of them. Their world was so close, but so far away. I don’t know sign language, so all I could do, when I allowed myself to peek over at them, was guess at what their discussion might be about. A man and a woman, each maybe twenty-five or so, talking very passionately about something that was, to me, utterly mysterious.

Encountering those two people today made me deeply happy. I gave thanks to God that I had been able to observe them. Their faces, turned to one another as they shared their hearts through their eyes and hands, were like the ones I used to see years ago on parallel-running trains. Human faces. Not masks. Horizons of the infinite dignity of the Other. I will keep looking out of train windows in the Tokyo night to see if there are still other faces in other trains, open to encountering the mystery of another human person, waiting in turn for someone else to encounter them.