In the Austrian Basement case, I introduced a scenario that, I think, is difficult to analyze in good faith while rejecting the asymmetry. If absent pain were not good, why should we feel a sense of relief should E. F. decide to use the birth control? If absent pleasure were not a much lesser moral consideration - were it not in fact merely neutral or not good, but not bad either - why should we feel horror at the prospect of babies being born into the dungeon?
This is especially important for those who still cling to the "non-identity problem" as a genuine problem. "How can a baby be harmed by being born into the dungeon? Before the baby is born, there's no one to be harmed! And if no one is harmed, it is not a wrong. So procreate away!" But, of course, it is wrong. We have a duty to avoid creating babies in dungeons. To demand that there be someone to be harmed before we recognize a wrong strikes me as a bit silly. I am with Professor Benatar that it is enough that an outcome be bad for a person, in the sense of worse than the alternative (nonexistence), to qualify the bringing about of that outcome as a wrong.
In the case of Slum World, I attempted to put a concrete face on the so-called "repugnant conclusion" of aggregate well-being measures, and to demonstrate that the claim that nonexistent people have for happiness/existence is weak (that absent pleasure, if someone is not thereby deprived, is merely neutral). The prospective inhabitants of Slum World do not have a strong claim to come into existence. The nonexistence of their pleasures is merely neutral, and the nonexistence of their pain is just good. This is true even though, once born, the inhabitants of Slum World would presumably choose to keep living (lead lives worth continuing). Low Population Splendor World is good, Slum World is awful, and rejecting the asymmetry seems to require one to claim otherwise.
Coming into existence is sui generis, and it is difficult to construct clear examples to use in testing intuition that aren't just different situations of bringing people into existence. My last example, below, attempts to illustrate something like the asymmetry without being about bringing people into existence.
3. Commercial Children's Television
An advertisement for a new children's toy runs several times per hour on a commercial children's television program. The advertisement creates a desire for the toy in the children who see the commercial. Of these children, many of them will eventually receive the toy from their parents, but others will not. Still other children, cruelly brought to life in the households of liberal academics, do not have televisions and therefore do not see the advertisement, and never desire the toy at all.
a. Which group out of the three is best off?
b. Do television advertisers actually do children good by creating desires that might later be fulfilled?