Everyone that you've known at all well has been of above average intelligence, and most probably in the top quartile or quintile at the least. The world of the averagely intelligent is remote from you, except perhaps at the gym. Intelligence, that is, IQ, is normally distributed, so that for every superior person in your milieu there is roughly speaking an equivalently inferior person somewhere in the population. Of course the worlds of the bright and the dull are far from mirror images of each other, and there is no causal relation between the two, but in some sense they are interdependent in that your world could not be what it is without being braced, as it were, against that other world. If you stayed where you were but the mean IQ moved up or down, or the standard deviation narrowed or broadened, you would find yourself in a very different world. Contemporary utilitarians have jettisoned the idea of a roughly quantifiable happiness for that of a roughly quantifiable life-worth, as in the (metaphysically doubtful) phrase 'a life worth living'. But can you ever know if your life is 'worth living'? Imagine someone whose entire life is one of deeply rewarding altruism, but where the limits of their circle of care only extends as far as their own community, which, it turns out, can only exist because of the enslaving and oppression of another far more numerous community. You might say that while on a subjective whole-of-life assessment their life is eminently worth living, objectively, since it would have been better for them not to have existed at all, their life was not worth the living. It depends on how far the circle of empathy extends, and this is a matter of epistemology and therefore somewhat arbitrary and subject to indefinite revision. An alien intelligence may be aware of interdependent forms of suffering that no human mind can grasp. All of which is to say that nothing in experience can ever serve to refute the nihilist proposition that it would have been far better never to have existed at all. The same argument admittedly also works in reverse. Suffering is as inconclusive as happiness, but it is rather more persuasive.