Say Jane develops a brain tumor that cannot be removed and causes her to experience unrelenting physical pain. She cannot live a productive life and must stay in bed for the rest of her life. Most people, it seems, would say that Jane would be "better off dead," and that her escape from her pain would be a good thing despite her no longer existing.
But can Jane really be better off not-existing? Does this actually make any coherent sense?
I don't think it does, and I believe this does not have as much of an impact on our axiological judgments than it seems to commonly be said, and in fact leads us to a more well-founded axiology. Strict literalism is not as problematic as it may seem.
So say we pull the plug, and Jane dies. One month later we learn that the data surrounding Jane's condition was accidentally messed up with an actually terminally ill patient, and that had Jane gotten a surgery on her brain, she could have recovered in less than a week and led a productive and relatively comfortable life.
Suddenly it doesn't look like Jane was actually better off dead. She missed out on a potentially nice future: in Jane's case, it was between non-existence and a relatively enjoyable existence. Surely a personally-enjoyable existence would be better than not existing at all?
What we have here, then, is an inconsistency - non-existence becomes the better option so long as no "good" future in which one exists is possible. But as soon as this does become possible, the value "switches" to favoring existence, because someone actually exists.
To put it another way: Jane exists and is in great pain. We have two options: mercy kill her, or help her recover. Both outcomes result in Jane not experiencing any pain, but clearly they are not morally equivalent. We would not mercy kill someone if there is a chance they could get better and continue existing.
The reason for the difference here seems to me to be the existential condition of Jane. Had Jane not existed, she could not be in a better state, because she would have existed (however it can still be better for Jane to continue existing, because she would exist).
The apparent trouble arises when we wonder what we should do if Jane had no other options between a life of misery and non-existence. If we can't apply a "better" value to the non-existence of Jane, then what justifies the intuitive belief that Jane ought to no longer exist, for her own sake?
Existential literalism has not sunk quite yet, though. Instead of focusing on "better" or "worse" relationships in these sorts of conditions, we ought to focus on "worthiness" values. Such worthiness conditions will inherently depend on a positive existential condition of the subject. Is Jane's life of continual misery "worth" continuing? No, because the future she has in store has little to no redeeming qualities. Would Jane be "better off" dead? No, because she wouldn't exist. But this, I claim, has no relevance here: we should focus on getting Jane into a better situation and out of a worse situation, and if we cannot accomplish the former then the latter changes from getting out of a worse situation to eliminating situations entirely.
It's a difficult idea to explain, so reiterate it another way: we should not be focusing on removing the bad because its absence would be good, but rather, we should be focusing on removing the bad because it is bad. The act of removing the bad is
And this works well with the scenario described above, in which we can either mercy kill Jane or help her recover. We should focus on removing the bad and adding the good, which explains why we shouldn't mercy kill Jane; for although we would be removing the bad, we would not be adding the good that we could be. That is not the best course of action, and it would be wrong to not take it (for additional reasons as well, of course).
Thus the existential literalist position holds value as wholly immanent in existence. Indeed it seems to be the case that looser axiologies are rather ad hoc: we don't kill terminally-ill people because they would be in a better state, but because they don't have a life worth living. It is not until the person has died that people start coping by saying "they're in a better place now" (as if the person is now in some peaceful, happy slumber or playing basketball with Jesus), because the reality is that they are not in a better place, they aren't even anyone anymore. Which makes scenarios like these that much more tragic, because there is no happily-ever-after conclusion. Jane either lives a life of horrible pain, or doesn't live at all. That doesn't look like a good scenario to me.