PROFUNDUS

Below about two hundred metres, the sea begins to lose its light. Below a thousand, the light is gone completely. From there down to the bottom of the deepest trench, nearly eleven kilometres under the surface, lies the largest living space on the planet, and almost all of it is permanently dark.

We know surprisingly little about it. Only around a quarter of the ocean floor has been mapped in detail. Deep-sea expeditions still come back with animals nobody has seen before: fish that make their own light, colonial creatures longer than a bus, whole communities living on the heat of volcanic vents without ever touching sunlight.

Heraclitus never saw the deep sea, but he knew about depth. You could travel every road, he wrote, and still not find the limits of the soul, so deep is its measure. He lived in Ephesus around 500 BC, wrote in riddles and was nicknamed the Obscure. On this point, though, he is unusually clear. There is more in a person than any journey can cover.

Modern neuroscience would agree. The brain holds around eighty-six billion neurons, each connected to thousands of others, and most of what happens there never reaches awareness. We live on the lit surface of ourselves, a thin layer of thoughts and plans, and beneath it lies a great dark volume we rarely visit.

Sometimes we are pulled down there anyway: by grief, by love, by a sleepless night, by a piece of music that goes further in than expected. It can be frightening. The pressure is real, the light is gone, and the familiar shapes dissolve.

The deeper you go, the less you see, and the more you find.

Divers describe the moment when the light from the surface fades and they switch on their own lamp. Everything they see from then on is lit by what they brought down with them. Going into the depths of a life is similar. Nobody else's light reaches that far.

PROFUNDUS moves at that pace: slowly, with weight, into a space where the usual sounds fall away. It does not try to bring anything back to the surface. It stays down long enough for the eyes to adjust.

— Heraclitus of Ephesus, c. 535–475 BC