Imagine a world with an ever diminishing number of sentient beings. In most antinatal settings such a world would become increasingly better. This is the case if we leave out of account such settings under which the suffering of the remaining sentient beings increases geometrically along with the diminishing number of sentient beings (due to diminishing mutual aid when there are only few humans left, this under the improbable premise that a human will be the last sentient being).
At some point in time this world will be inhabited by only one being capable of negative sentience – the famous ‘last of the race’. Such a world we would label as extremely good compared to a world inhabited by billions of beings capable of negative sentience.
Let us have a closer look though at how we are to evaluate this world with the demise of the last sentient being. No negativity whatsoever will be experienced in this world after the last death has taken place. Has this world become the best of all possible worlds under antinatal auspices? At first glance we’re inclined to saying yes. At the same time, however, rather than the best of all possible worlds, this world would have become ethically neutral in an antinatal setting (and not only within the framework of antinatalist moral theory but according to any ethics impregnated by utilitarian thoughts). Even though such a fictitious world would be open to esthetical evaluation, the raison d’être for ethical evaluation would have vanished with the last being capable of negative sentience.
An apparent solution to the antinatalist-improvement paradox would be pointing out to other inhabited worlds: With the demise of the last sentient being on our planet the universe would with all probability have become better since we have good reason to assume that there are many other planets inhabited by sentient beings capable of negative experiences. However, reading the term “world” as “planet” does not help much further if we proceed to interpreting “world” as the sum of all sentient beings in the universe: With the demise of the last sentient being the universe wouldn’t have become ethically the best of all possible worlds but ethically neutral. Still we seem entitled to say that such an ethically neutral world is better than a world inhabited by beings capable of negative experiences.
What about a UNIVERSE A inhabited by beings capable solely of positive experiences? Is such a world better than an ethically neutral UNIVERSE B void of all sentience? From the point of view of an IMPOSSIBLE OBSERVER (since self-refuting) of UNIVERSE B it is not the case that UNIVERSE A is to be deemed better – since there can be no motivation to create positively sentient beings for their own sake.