Abstract

My aim in this essay is to shed light on the origins of Peircean vagueness. The intention is therefore primarily historical-philological, exploring the logical-semiotic roots of vagueness. First, I distinguish the two senses in which Peirce treats the notion of vagueness: one referring to the subject, the other to the predicate within a proposition, specifying that I am only concerned here with the first sense of vagueness. Second, I argue that Brock and Chauviré, while attempting to unravel the origins of Peircean vagueness through the notion of the _individuum vagum_, fail to fully resolve the problem. Third, I expound the medieval theory of _suppositio_, which concerns the denotation and quantification of the propositional subject. This medieval logical theory aimed to clarify the meaning of indefinite and indeterminate propositions. Fourth, I present textual evidence in which Peirce demonstrates his thorough knowledge of the medieval theory of _suppositio_, Peter of Spain's theory in particular. In the same section, I highlight a neglected detail within R 530, in which Peirce directly refers to the origins of the notion of vagueness. Finally, I argue that once the quantifiers (existential and universal) were discovered and formalized, Peirce gradually lost interest in the theory of _suppositio_ as a useful tool for clarifying vague (indefinite) and general (indeterminate) propositions, since he had a better logical tool at his disposal.