Ethics is founded on evidence that can’t be shared. My experience of severe pain gives me reason to believe that nihilism is false. In other words, when I am in severe pain, that pain, as it’s presented to me, gives me evidence that it’s bad in some way. I can’t share this evidence with you; you can’t feel my pain. Even if you could peer inside my head and see it, you wouldn’t be presented with it in a way that gave you evidence of its badness. But you, of course, are in the same position regarding your pain: when you are in severe pain, that pain, as it’s presented to you, provides you with evidence that it’s bad in some way. So, each of us has evidence for his or her severe pain being bad in some way. In the case of infants and nonhuman animals, the evidence is there, but the creature is too unsophisticated to recognize it as such.
Stuart Rachels, Hedonic Value, Ph.D. dissertation, University of Syracuse, 1998, p. 35