How is it possible to know if someone has free will? If given a choice between A or B a person always chooses B, then we might think the person does not have free will because, like a machine, he or she always does the same thing in a given situation. Suppose that the person sometimes chooses A and sometimes chooses B. We might then think the person has free will, but why? Why do they sometimes choose A and other times choose B. Are their choices random? If they are not random, then are they responses to previous events? Would they always respond to those events in the same way like a machine would? Making decisions in a rational way can be done by a machine (If the temperature drops below 66°, turn the heater on. If the temperature rises above 70°, turn the heater off). It looks to me that the only way to tell if someone is exercising free will is if they behave erratically. Yet machines like the Lorenz Water Wheel can be built which behave erratically. I just don’t know.