Three claims wittgenstein makes in the tractatus are explicated viaschopenhauer's idealism: 1) ethical reward and punishment lie inthe action itself, 2) the good or bad exercise of the will alterthe world's limits, so that it waxes or wanes, 3) eternal life belongsto those who live in the present. schopenhauer's theory fills outsome of wittgenstein's statements. for example, the happy man's worldwaxes to the degree that he frees himself from the false perspectiveof the 'principium individuationis'. however, the link between schopenhauer'smetaphysics and his ethics is tighter than the analogous link inwittgenstein.
Goodman, R. B. (1979). Schopenhauer and Wittgenstein on Ethics. Journal of the History of Philosophy, 17(4), 437–447. https://doi.org/10.1353/hph.2008.0130