Logic may well be the single most important key to understanding Peirce's thought and influence. It was his deductive logic that brought him an international reputation in his lifetime and led to conspicuous references to his work by figures such as Peano, Schröoder, Russell, Venn, Jevons, and Clifford. Peirce's highest, and in fact only, academic position was as lecturer in logic at Johns Hopkins University. He himself said on numerous occasions - when he wasn't emphasizing his role as a working scientist with the Coast Survey, that is - that he was mainly a logician. He called his existential graphs his chef d'oeuvre. Logic, especially the logic of relations, played a central role in the development of his philosophy. His three Categories were based on, and shown to be fundamental by, the logic of relations. The logic of relations is central to his analysis of the fundamental triadic notion of his semeiotics, “__ signifies __to __.” He saw his theory of scientific method as just logic, broadly construed. And of pragmatism itself, he often repeated that it was nothing more than the ideal fixation of belief, and this was the very goal of logic.