Criticizing himself again, Sidgwick writes: I am not an original man: and I think less of my own thoughts every day.
Derek ParfitWhile reasons are provided by the facts,...rationality...depends instead on our beliefs. [...] [I]f I believe falsely that my hotel is on fire, it may be rational for me to jump into the canal. But I have no reason to jump. I merely think I do. And, if some dangerous treatment would save your life, but you don't know that fact, it would be irrational for you to take this treatment, but that is what you have most reason to do.
Derek ParfitIt is not enough to ask, 'Will my act harm other people?' Even if the answer is No, my act may still be wrong, because of its effects on other people. I should ask, 'Will my act be one of a set of acts that will together harm other people?' The answer may be Yes. And the harm to others may be great. If this is so, I may be acting very wrongly, like the Harmless Torturers.
Derek ParfitNormativity, I believe, is very different from motivating force. Neither includes, or implies, the other. Other animals can be motivated by their desires and beliefs. Only we can understand and respond to reasons.
Derek Parfit