This essay gives a new epistemological interpretation of G. Leopardi's "Dialogo di Cristoforo Colombo e di Pietro Gutierrez", based on the analysis of the peculiar philosophical language of this work and on the comparison - common in the seventeenth century - between Cristoforo Colombo and Galileo Galilei. Leopardi was familiar with this image of Colombo as one of the founders of the modern science, employing the "galilean" method of the empirical verification of theoretical conjectures. In this way, Colombo expresses Leopardi's theory of the progress and the method of science: the only possible progress in philosophy and science consists in the removal of errors, both the popular and the learned ones. Leopardi's nihilism is strictly connected with his rejection of the logical principle of contradiction. Beyond metaphysical and moral nihilism, there is gnoseological nihilism: error is the opposite not only of truth, but also of good; it is, at the same time, the structure of reality and the universal category of the human mind.