I chose the specialty of surgery because of Matron, that steady presence during my boyhood and adolescence. “What is the hardest thing you can possibly do?” she said when I went to her for advice on the darkest day of the first half of my life. I squirmed. How easily Matron probed the gap between ambition and expediency. “Why must I do what is hardest?”

“Because, Marion, you are an instrument of God. Don’t leave the instrument sitting in its case, my son. Play! Leave no part of your instrument unexplored. Why settle for ‘Three Blind Mice’ when you can play the ‘Gloria’?”

How unfair of Matron to evoke that soaring chorale which always made me feel that I stood with every mortal creature looking up to the heavens in dumb wonder. She understood my unformed character.

“But, Matron, I can’t dream of playing Bach, the ‘Gloria’ ... ,” I said under my breath. I’d never played a string or wind instrument. I couldn’t read music.

“No, Marion,” she said, her gaze soft, reaching for me, her gnarled hands rough on my cheeks. “No, not Bach’s ‘Gloria.’ Yours! Your ‘Gloria’ lives within you. The greatest sin is not finding it, ignoring what God made possible in you.”

I was temperamentally better suited to a cognitive discipline, to an introspective field—internal medicine, or perhaps psychiatry. The sight of the operating theater made me sweat. The idea of holding a scalpel caused coils to form in my belly. (It still does.) Surgery was the most difficult thing I could imagine.

And so I became a surgeon.

Thirty years later, I am not known for speed, or daring, or technical genius. Call me steady, call me plodding; say I adopt the style and technique that suits the patient and the particular situation and I’ll consider that high praise. I take heart from my fellow physicians who come to me when they themselves must suffer the knife. They know that Marion Stone will be as involved after the surgery as before and during. They know I have no use for surgical aphorisms such as “When in doubt, cut it out” or “Why wait when you can operate” other than for how reliably they reveal the shallowest intellects in our field. My father, for whose skills as a surgeon I have the deepest respect, says, “The operation with the best outcome is the one you decide not to do.” Knowing when not to operate, knowing when I am in over my head, knowing when to call for the assistance of a surgeon of my father’s caliber—that kind of talent, that kind of “brilliance,” goes unheralded.

On one occasion with a patient in grave peril, I begged my father to operate. He stood silent at the bedside, his fingers lingering on the patient’s pulse long after he had registered the heart rate, as if he needed the touch of skin, the thready signal in the radial artery to catalyze his decision. In his taut expression I saw complete concentration. I imagined I could see the cogs turning in his head; I imagined I saw the shimmer of tears in his eyes. With utmost care he weighed one option against another. At last, he shook his head, and turned away.

I followed. “Dr. Stone,” I said, using his title though I longed to cry out, Father! “An operation is his only chance,” I said. In my heart I knew the chance was infinitesimally small, and the first whiff of anesthesia might end it all. My father put his hand on my shoulder. He spoke to me gently, as if to a junior colleague rather than his son. “Marion, remember the Eleventh Commandment,” he said. “Thou shall not operate on the day of a patient’s death.”

I remember his words on full-moon nights in Addis Ababa when knives are flashing and rocks and bullets are flying, and when I feel as if I am standing in an abattoir and not in Operating Theater 3, my skin flecked with the grist and blood of strangers. I remember. But you don’t always know the answers before you operate. One operates in the now. Later, the retrospectoscope, that handy tool of the wags and pundits, the conveners of the farce we call M&M—morbidity and mortality conference—will pronounce your decision right or wrong. Life, too, is like that. You live it forward, but understand it backward. It is only when you stop and look to the rear that you see the corpse caught under your wheel.

Excerpted from Cutting for Stone by Abraham Verghese Copyright © 2009 by Abraham Verghese. Excerpted by permission of Knopf, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.