Modern medicine can accomplish a lot, but it can't save every life. Nor can it answer every question.
The ethics of medicine are examined by psychiatrist and bioethicist Jacob Appel in the book Who Says You're Dead? Medical & Ethical Dilemmas for the Curious & Concerned.
In the title example, who decides you are dead if you are being kept alive only by machines? If a test determines that a man's daughter is actually NOT his daughter, who does the doctor tell?
These hypotheticals and more make for a lively discussion of ethics in the healing arts.