Abū Bakr al-Bāqillānī (d. 403/1013) was a preeminent scholar and an influential participant in a diverse range of Islamic discourses. His texts are often studied within the context of individual disciplines, but I argue that a more comprehensive reading of his work uncovers significant connections between his various texts. This paper explores a major site of such interdisciplinary thinking through looking at al-Bāqillānī’s discussions of bayān in his writings on legal theory and the inimitability of the Qurʾān. In his book of legal theory entitled al-Taqrīb wa-l-irshād fī uṣūl al-fiqh, al-Bāqillānī defines bayān as being equivalent to dalīl (indicant). This definition of bayān is broad enough to include any meaningful utterance—not only those that clarify other opaque utterances, as many scholars including al-Shāfiʿī claimed. Al-Bāqillānī employs his broad definition of bayān to theorize a system of language where all utterances clarify meanings and are understandable according to the same rules. Thus, whereas for some exegetes, Q 3:7 excludes some verses from human understanding, for al-Bāqillānī all sound utterances are clear, both in human and divine speech. Al-Bāqillānī also expounds on the idea of bayān in an important but often overlooked part of his Kitāb Iʿjāz al-Qurʾān in which he draws a distinction between rhetorical features that contribute to the Qurʾān’s miraculous inimitability as compared to those that do not. Bayān is one of the categories of textual features where al-Bāqillānī says iʿjāz is found. Building on his assertion that the entire Qurʾān is bayān, here too al-Bāqillānī argues that the Qurʾān is clear, understandable, and entirely interpretable by humans. In both discourses, al-Bāqillānī theorizes bayān in ways that support his larger scholarly goal of synthesizing Islamic disciplines to create a consistent Islamic system of thought. By using the concept of bayān to assert the clarity of the whole Qurʾān, al-Bāqillānī sets Islamic exegetical discourses on solid footing. Theorizing revealed language as understandable to humans renders scriptural interpretation valid. This paper brings to light al-Bāqillānī’s contribution to developing conceptions of bayān, taking into account his adaptation of earlier definitions and the elements of his thought on bayān adopted by his successors, including ʿAbd al-Qāhir al-Jurjānī and Fakhr al-Dīn al-Rāzī. By way of conclusion, I offer some thoughts on bayān’s prominent role in medieval discussions of Qurʾānic style and Islamic legal theory as well as al-Bāqillānī’s role in furthering the development of bayān as a key concept in Arabo-Islamic thought.