but the critical level c is variable, and can depend on the choice set. So suppose the choice set consists of two situations. In the first, I exist and I have a positive welfare (or utility) w>0. In the second case, I don’t exist and there is another person with a negative utility u<0. His relative utility will also be u’<0. For any positive welfare I can pick a critical level c>0, but c<w-u’, such that my relative utility w-c>u’, which means it would be better if I exist. So you turned it around: instead of saying “for any critical level c there is a welfare w...”, we should say: “for any welfare w there is a critical level c...”
but the critical level c is variable, and can depend on the choice set. So suppose the choice set consists of two situations. In the first, I exist and I have a positive welfare (or utility) w>0. In the second case, I don’t exist and there is another person with a negative utility u<0. His relative utility will also be u’<0. For any positive welfare I can pick a critical level c>0, but c<w-u’, such that my relative utility w-c>u’, which means it would be better if I exist. So you turned it around: instead of saying “for any critical level c there is a welfare w...”, we should say: “for any welfare w there is a critical level c...”