This paper uses Stoic theory of language to gain more insight into Roman lawyer Proculus’s legal opinions on the meaning and understanding of ambiguous testaments, wills and dowries. After summarizing Stoic theory of language, the paper discusses its reception in Roman jurisprudence and situates Proculus in a Stoic legal/philosophical context. The meat of the article lies in the re-examination of Proculus’s legal opinions on ambiguities in light of Stoic theory of language, through: (1) the analysis of a case demonstrating that Proculus’s embeddedness in Stoic doctrine went beyond his technical competence in propositional syllogisms, going into the territory of Stoic physical materialism and, (2) the investigation of four cases that reveal how his approach to problems of ambiguity in unilateral legal acts converges with the Stoic conception of the parallelism between speech and thought.