When a man goes through six years training to be a doctor he will never be the same. He knows too much.

Bagnold’s remark treats medical training as a one-way transformation: prolonged exposure to anatomy, illness, and mortality alters a person’s ordinary relationship to the body and to everyday life. “He knows too much” suggests that clinical knowledge is not merely empowering; it can also be burdensome, stripping away comforting ignorance and making the doctor perpetually aware of hidden vulnerabilities in others and in himself. The line hints at a social distance created by expertise—once you have seen what lies beneath the surface (literally and figuratively), you cannot fully return to naïve perceptions. It also carries an ambivalence about professional formation: education confers authority, but at the cost of innocence and uncomplicated feeling.