This came to me when I was lying awake in bed at night. Consider a biologically immortal person (meaning not susceptible to disease, age, or etc, but can die from physical wounds) locked alone in a room with a knife for all time (henceforth called a "BIPLRAT"). P1: If a BIPLRAT has free will, then he can choose not to kill himself. P2: If a BIPLRAT has free will, then it is possible that he can kill himself. P3: If it is possible that a BIPLRAT can kill himself, then given enough time, he *must* kill himself (this premise comes from the so called "infinite monkey theorem." Here is an overview: http://en.wikipedia.org/wiki/Infinite_monkey_theorem) C: Therefore, if a BIPLRAT has free will, he must kill himself. Which of course is a contradiction because a person with free will must have the option to not kill himself.