Derek Parfit’s long-awaited work On What Matters is a very ambitious, very strange production seeking to defend both a nonreductive and nonnaturalistic but nonmetaphysical and nonontological form of cognitive intuitionism or rationalism and an ethical theory (the Triple Theory) reflecting the convergence of Kantian universalizability, Scanlonian contractualism, and rule utilitarianism. Critics have already countered that Parfit’s metaethics is unbelievable and his convergence thesis unconvincing, but On What Matters is a truly Sidgwickian work, the implications of which largely remain to be worked out. Parfit does not go far enough in spelling out exactly what matters and why, what normative reasons we actually have, and where we should go from here, if we take him seriously.