This paper takes as its starting point the Kitāb ithbāt al-waṣiyya lil-imām ʿAlī b. Abī Ṭālib attributed to al-Masʿūdī. This attribution was deemed improbable by Charles Pellat and this view seems since to have held consensus. What I intend here is not primarily to revise Pellat’s verdict, rather to dwell on an intriguing aspect of tenth century Imāmism which this text and its attribution throws into relief. This is a certain dichotomy amongst prominent Imāmī authors in 10th century Baghdad and its Buwayhid environs. On the one hand, several of the era’s great polymaths, hailing from Buwayhid society’s effervescent intellectual scene, seem to have been Imāmīs, with al-Masʿūdī as well as al-Miskawayh and Ibn al-Nadīm being prominent examples. On the other hand, the writings which are usually considered to hold the reins of a distinct Imāmī identity at this time are those of muḥaddithūn such as Ibn Bābawayh and al-Kulaynī, whose work is considered by and large as representing a naïve, traditionalist Imāmism prior to its rapprochement with Muʿtazilī kalām and the ḥadīth criticism of the emerging Sunnī madhāhib. A picture thus emerges of an Imāmī thought which seems paradoxically to lag behind the erudition of some of its more intellectually prominent adherents. This state of affairs meanwhile draws attention to potential fault-lines in the academic study of this period; seldom do litterateurs like Masʿūdī feature prominently in studies of Shīʿī thought at this time, nor does views of Buwayhid ‘humanism’ long consider the Imāmī beliefs of many of its most noteworthy exemplars. At the root of this apparent dichotomy is the fact that different Imāmīs of this period were producing very different kinds of literature. In this regard the Kitāb ithbāt al-waṣiyya represents a tantalizing opportunity; here we have a text attributed to a great adīb which participates in the traditionalist discourse of the muḥaddithūn. If it is genuine it thus represents an arguably unique example of an author writing at both ends of the spectrum. What I shall therefore be asking is whether these different types of composition merely represent different choices of genre (be they determined by circumstantial factors or personal whim) or whether they enact real contradictions between competing systems of knowledge. In asking in these terms whether the book could have been written by Masʿūdī, I hope that this fascinating text may shed light on relations between knowledge production and sectarian identity in this period.