He chose medicine to study meaning, not just biology

Kalanithi's path to neurosurgery ran through literature, not straight through science. He'd studied English and human biology at Stanford, then philosophy of science and medicine at Cambridge, driven by a specific question: what makes human life meaningful, and where in the machinery of the brain does meaning actually live?

He concluded that literature alone couldn't answer this — that he needed direct, clinical contact with the brain and with mortality to understand identity at the point where biology and selfhood meet. Neurosurgery, uniquely among specialties, put him constantly at that intersection: a surgeon operating on the brain is operating on the physical substrate of a person's very self.

This choice of career, made years before his diagnosis, reads retrospectively as a kind of preparation — a life spent studying, at a professional distance, the exact questions he would later have to answer personally.

Takeaway: the questions you're drawn to early in life are often more prophetic than you realize at the time.