Men were made for higher things, one can’t help wanting to say, even though one knows that men weren’t made for anything, but are the product of natu… - J. J. C. Smart

I want to illustrate the relevance of metaphysics to ethics by reference to what is the greatest moral problem that has ever faced the human race: the question of nuclear war...the threat of nuclear war makes us envisage macro effects (effects on all people and the whole earth): the end of the human race, perhaps also of mammalian life itself, and the end of the prospect of humans evolving into yet higher and more wonderful forms of life...Those who comfort themselves with the thought that mutual deterrence has kept the peace for thirty years forget the importance of low probabilities in the macro context. Indeed what does it matter, from the perspective of possible millions of years of future evolution, that the final catastrophe should merely be postponed for (say) a couple of hundred years? Postponing is only of great value if it is used as a breathing space in which ways are found to avert the final disaster. And even a small probability that we shall not have this breathing space will yield negative expected utility of macro dimensions.

Certainly there would be no future suffering on earth if all life on earth ceased. But most people seem glad that they were born: we do not usually think of present people (and animals) that the pain in their lives outweighs their pleasures...There have been great advances in the human condition due to science: recollect the horrors of childbirth, surgical operations, even of having a tooth out, a hundred years ago. If the human race is not extinguished there may be cures of cancer, senility, and other evils, so that happiness may outweigh unhappiness in the case of more and more individuals. Perhaps our far superior descendants of a million years hence (if they exist) will be possessed of a felicity unimaginable to us.

The sentiment to which [the utilitarian] appeals is generalized benevolence, that is, the disposition to seek happiness, or...good consequences, for all mankind, or perhaps for all sentient beings.