When I can’t sleep, I read children’s books. One night, I discovered In the Half Room (public library) by Carson Ellis in my tsundoku — an impressionistic invitation into a world where only half of everything exists.

Leafing through this quietly delightful treasure, I had a flash memory of a passage from The Man Who Mistook His Wife for a Hat (public library) — the 1985 classic in which Oliver Sacks staggered the modern mind with revelations of how the brain’s fragility renders reality itself fragile.

One of the cases he relays is that of a bright woman in her sixties called Mrs. S., whose right hemisphere was savaged by a massive stroke. Although it left her with “perfectly preserved intelligence — and humor,” it also left her living in only half the world:

She sometimes complains to the nurses that they have not put dessert or coffee on her tray. When they say, “But, Mrs. S., it is right there, on the left,” she seems not to understand what they say, and does not look to the left. If her head is gently turned, so that the dessert comes into sight, in the preserved right half of her visual field, she says, “Oh, there is it — it wasn’t there before.” She has totally lost the idea of “left,” with regard to both the world and her own body. Sometimes she complains that her portions are too small, but this is because she only eats from the right half of the plate — it does not occur to her that it has a left half as well. Sometimes, she will put on lipstick, and make up the right half of her face, leaving the left half completely neglected: it is almost impossible to treat these things, because her attention cannot be drawn to them and she has no conception that they are wrong. She knows it intellectually, and can understand, and laugh; but it is impossible for her to know it directly.

Termed hemi-inattention in the 1950s when it was first clinically described, this condition is now better known as hemispheric neglect or unilateral neglect. A year after The Man Who Mistook His Wife for a Hat was published, the physician M. Marsel Mesulam captured its startling semireality in his book Principles of Behavioral Neurology:

When the neglect is severe, the patient may behave almost as if one half of the universe had abruptly ceased to exist in any meaningful form… Patients with unilateral neglect behave not only as if nothing were actually happening in the left hemispace, but also as if nothing of any importance could be expected to occur there.

What makes neurological disorders so fascinating is that their abnormal physiology is often a microcosm of the psychological pitfalls of the healthy brain. Who hasn’t shuddered with a flash of aphasia, suddenly unable to retrieve the right word or formulate a thought into a coherent sentence when in shock or in awe or tired to the bone? Hemispheric neglect menaces our sense of reality with the intimation that we too may be missing entire regions of reality because our attention simply cannot be drawn to them.

Perhaps we too are living in the half room.

And how can it be otherwise, given we are creatures of emotional incompleteness capable of extraordinary willful blindness, going through our days half-aware of our own interior, the other half relegated to an unconscious which our dreams, if we remember them, and our therapy, if it is any good, hint at but which remains largely subterranean. How, then, can we expect to have a complete picture of anything or anyone else?

There is no half room more extreme than infatuation. In those delirious early stages of falling in love, we magnify the positive qualities of the beloved to a point of crystalline perfection, turning a willfully blind eye to their shortcomings, only to watch the shiny crystals slowly melt to reveal the rugged reality of the actual person — imperfect and half-available, for they too are half-opaque to themselves.

To come to love someone after being in love with them is to be willing to walk the full room from corner to corner across every diagonal, to run your fingers over the floorboards and love every splinter, to run your gaze over the ceiling and love every crack — not because you love the pain and the leakage, but because you love the totality of the person, that incalculable sum we call a soul.

Mrs. S., intelligent and determined, refused to let her condition shape her experience of reality and developed a simple, brilliant compensatory strategy: Each time she knew something was there but she could not find it, unable to look left and therefore to turn left, she would turn right and rotate 180 degrees until it came into view. Suddenly, the hospital food portions she felt were too small doubled to their full size and she felt sated.

The trick, of course, is to be intelligent enough and humble enough to recognize that you might be missing half of reality.