There is a body of texts in Arabic the language of which has traditionally been called 'Middle Arabic' (MA). The term persists, although often taken to relate to chronological and historical 'middleness' rather than linguistic intermediacy. One perhaps less well-known text composed in this style is Ibn al-Mujāwir's thirteenth-century Tārīkh al-Mustabşir. As is typical of so-called 'MA' texts, Classical Arabic (CA) appears to dominate the style, with many non-CA features mixed into the CA base. Often, the non-CA features are essentially typical of Spoken Arabic (SA), so that the language is generally said to be a mix of CA and SA. There are, however, many non-CA features of Tārīkh al-Mustabşir that do not conform entirely to either CA or SA, yet their use is not unsystematic. For these reasons we reject the term 'MA' in favour of 'Literary Mixed Arabic' (LMA). This paper presents the results of the pilot study of our project, which centres on the question 'what is Literary Mixed Arabic?' Our study takes some of the morpho-syntactic variables that have been argued to differentiate CA from SA against which to test systematically the language of the text. In this context, these variables can be seen as features according to which the norms of CA and the norms of (a given variety of) SA are highly likely not to be compatible. Thus, we take such variables to reveal a systematic divergence between two grammars, or in effect, points at which they clash. We use these differential variables to explore the hypothesis that the features of the text that are not entirely compatible with the norms of CA and/or SA arise from the particular strategy employed to resolve a clash between the two grammatical systems.