This book charts the dissipation of an authoritative moral framework from the intersubjectivism and universalism of Immanuel Kant to the nihilism of Nietzsche. Weber’s much vaunted polytheism is shown to be an heterogeneity of values, the reduction of morality to value judgements. The book proceeds to argue the case for the importance of St Thomas Aquinas’ epistemological realism, rationalist metaphysics of being and natural moral law as supplying the objective foundations capable of resolving the impasse of morality in the modern world. A Thomist reading reveals that Kant sought not to reject virtue, but to place virtue ethics on a rational foundation. The problem is that Kant’s commitment to the highest good is undermined by Kant’s rejection of rational metaphysics, cutting his moral law off from its foundation in ontological nature. Kant’s self-legislation of practical reason amounts to no more than the self-sufficiency of reason. I argue that this fails to supply a secure foundation for Kant’s ethics of the summum bonum. Kant is ultimately agnostic on the good, on account of his separation of reason from ontological nature. In time, Kant’s intersubjectivism and universality degenerates into the myriad relativisms, subjectivisms and nihilisms that inhabit the modern world. The book thus argues the case for the philosophical/theological synthesis of St. Thomas Aquinas as providing the only secure basis for the objective and universal foundations of the moral law and the common good. I argue that to make good Kant’s moral claims, we need to recover St Thomas Aquinas’ natural moral law, rationalist metaphysics and realist epistemology. I argue that the universal claims of the greatest of the modern moral and political philosophers – Rousseau, Kant, Hegel and Marx – can only be realised by being grounded in the natural law.