The mediaeval Islamicate world was dominated by a language-obsessed culture that placed great value on words and their meanings. These words and meanings could, for those who used them, make the difference between both earthly success or failure, and salvation or damnation in the hereafter. Scholars were also conscious of the contingency of the links between words and their meanings, and the potential this created for ambiguity. This dissertation is about the mechanisms, models, and assumptions those scholars used to manage linguistic ambiguity. My investigation focuses on ar-Rāġib al-Iṣfahānī (fl. ≤ 409/1018), one such language-obsessed scholar. I provide a comprehensive review of his life, works, and times. He put together a portfolio of intellectual positions in exegesis, theology, ethics, and poetics that was guided by a philosophy of language which accepted and negotiated linguistic ambiguity. Underpinning that philosophy was a theory of meaning that used the pairing of expression and idea (lafẓ and maʿnā) to deal with polysemy, the intent of the speaker, and the function of the lexicon. Ar-Rāġib’s philosophy was emblematic of what I call the Arabic Language Tradition, the shared assumptions of which constituted an indigenous philosophy of language that was able to supply its own answers to the central questions of linguistics and then use those answers across all of the genres encompassed by its scholarship, from grammar to poetics, law, and theology. It was an Arabic Language Tradition that is best understood through comparison to an alternative Classical Language Tradition that had its roots in the Organon and a theory of meaning with little space for ambiguity. Re-telling Islamic intellectual history through the lens of language in this way shows us that in addition to the well-known and oft-studied Islamic engagement with Hellenistic philosophy there was another, indigenous, tradition with its own answers to the problems of mediaeval scholarship. This Arabic Language Tradition saw in language a solution to these problems, rather than seeing language as just another hurdle to be overcome. / Near Eastern Languages and Civilizations