The eleventh century H?alab? scholar, politician and poet, Ibn Sin?n al-Khaf?j?, student of the famous Ab? al-?Al?? al-Ma?arr?, owes much of his acknowledgment to early thirteenth century’s D?iy?? al-D?n Ibn al-Ath?r. The latter, in his introduction to al-Mathal al-S??ir, adverts to the work of Ibn Sin?n titled Sirr al-Fa???a ‘The Secret of Eloquence’ as one of the two most important books on what Ibn al-Ath?r calls ?Ilm al-bay?n ‘the science of clarity [of expression]’. Especially consequential are regarded al-Khaf?j?’s deliberations on ‘sounds’, ‘phonemes’ and ‘the single word’, of which the latter is markedly influential in Ibn al-Ath?r’s voluminous work. And yet despite the association of the treatment of ‘the eloquence of the single word’ with al-Khaf?j? – to which indeed the entry Fa???a in the Encyclopaedia of Islam may attest – his overall approach to the study of kal?m ‘discourse’ is otherwise marginally treated, very much until this day (his absence from I?s?n ?Abb?s’ monumental survey of the history of Arabic literary criticism is a case in point). The aim of this paper is to closely analyze al-Khaf?j?’s Sirr al-Fa???a so as to understand its structure and logic, try to identify its sources and establish both its uniqueness and, no less important, commonness. Somewhat along the lines of George Kanazi’s study of K. al-S?in??atayn of Ab? Hil?l al-?Askar?, this paper ultimately purposes to situate the work of al-Khaf?j? within the pre-Sakk?kian, or pre-systematic, ‘Bal?gha’ tradition. The conception of Bal?gha or Fa???a as an ?ilm ‘science’ is already quite explicit in Sirr al-Fa???a, although al-Khaf?j?’s implicit objects of study are the distinctly delineated crafts of Ta?l?f al-kal?m ‘the composing of discourse’ and Naqd al-kal?m ‘the criticizing of discourse’. Though usually not exhibiting original data, and indeed being overshadowed by his contemporary ?Abd al-Q?hir al-Jurj?n?, I intend to show al-Khaf?j?’s holistic attitude toward the study of eloquence, encompassing the ontological understanding of language (inspired by Mu?tazilite thought) in addition to the linguistic one. Especially intriguing I find the role grammar plays within al-Khaf?j?’s theory of discourse, as a concept like Isti??ra ‘metaphor’ is subsumed under the category termed Wa?? al-alf?z maw?i?ah? ‘putting words in their [proper] place’ – a designation carrying a strong syntactic connotation and dating all the way back to S?bawayhi. Through this question I hope to expound the idea of the grammaticality of discourse in al-Khaf?j?’s work, pertaining to semantic and pragmatic grammaticality rather than a syntactic one.