This article compares two groundings of ethics: the ethical postulates of Immanuel Kant with the existential thinking of S. Kierkegaard. To achieve this goal, first, it proposes highlighting the fundamental ideas of Kantian ethics; then, secondly, highlighting Kierkegaard’s ethical stance; and finally, contrasting both approaches to identify differences and similarities. Conclusively, we can say that the pure Kantian ethical formality of duty for duty’s sake necessarily dispenses with existential and concrete content; it is an ethics that is grounded in itself, (...) that refers to itself, to the rational nature of the human being and its universality. In contrast, Kierkegaardian ethics is a Christian ethics, it is the ethics of love for one’s neighbour and, above all, for God; it is a relational and existential ethics of the single individual. (shrink)