Mortal Lessons is a 1976 book by Dr. Richard Selzer about his experiences as a surgeon.
Throughout the book, Selzer refers to the act of surgery as a deeply personal, almost religious affair. He references mythology and religion to show the comparisons:
Consider. The site of our internal organs is denied us. To how many men is it given to look upon their own spleens, their hearts, and live? ... I follow his gaze upward, and see in the great operating lamp suspended above his belly the reflection of his viscera. There is the liver, dark and turgid above, there the loops of his bowel winding slow, there his blood runs extravagantly. It is that which he sees and studies with so much horror and fascination. Something primordial in him has been aroused -- a fright, a longing. I feel it, too, and quickly bend above his open body to shield it from his view. How dare he look within the Ark! Cover his eyes!
(Selzer, Mortal Lessons, Google Books)
Selzer refers to the Ark of the Covenant, a holy object created by the Jews in Biblical times to house God's spirit on Earth. No ordinary man was able to look upon it and live. In a similar sense, the inside of the body is a secret place; it is not meant to be exposed, and in performing surgery Selzer is invading a human's most sacred privacy, that of their own body. In seeing his own interior, the patient is aware for the first time how fragile his life is, and how allowing Selzer to operate will save that life. The cost, since he was able to see inside himself, is the knowledge of his own mortality. In that sense, Selzer invades the privacy of a human body to save it, and is forgiven for his invasion with the reward of saving a life.