• Theoretically, I grant you, there is no possibility of error in necessary reasoning. But to speak thus "theoretically," is to uselanguage in a Pickwickian sense. In practice, and in fact, mathematics is not exempt from that liability to error that affects everything that man does.

    Charles Sanders Peirce (1992). “Reasoning and the Logic of Things: The Cambridge Conferences Lectures of 1898”, p.167, Harvard University Press