Complex sentence: He attributes these flaws to a "more fundamental problem" with utilitarianism: "the basic reason for following it is hollow", and he attacks John Stuart Mill's proof of utilitarianism as "not logic at all".
Split into simpler sentences: He attributes these flaws to a "more fundamental problem" with utilitarianism: "the basic reason for following it is hollow". He attacks John Stuart Mill's proof of utilitarianism as "not logic at all".