International audience ; In the Arabic hypothetical systems, a fa-appears very often between protasis and apodosis. According to Classical Arabic grammar, formed on preclassical corpus and for the sole operator in of the hypothetical systems, this fāʾ would mark a formal break as soon as the apodosis cannot be protasis, that is to say when the apodosis is not faʿala (neutral perfect from the point of view of time) nor yafʿal (imperfect apocopate). However, in addition to the innumerable cases where this rule is not respected, fāʾ often missing where it was expected, its appearance does not correspond only to a formal necessity, but also seems to match with a semantic one: it indicates that in its presence the relation between protasis p and apodosis q is not a matter of Logic but of Pragmatics. To put it another way with Larcher, fāʾ is functionally and fundamentally a segmentator which marks a pragmatic break indicating that the utterance is at the level of the natural logic of speech acts where the utterance of p is a cause for the utterance of q. There, different interpretative values can be glimpsed (concessional, deductive, justifying, oppositive, etc.). This paper sets out to add one more, that is a causalo-inductive value, and to show how, after recalling a fundamental distinction made by the medieval Arab tradition which distinguishes between fāʾ sababiyya (causal fāʾ) and fāʾ taʿlīliyya (illative fāʾ), the hypothesis of a correlation between the type of apodosis, depending on whether it is semantically an assertion (iḫbār) or not, and then a performative (inšāʾ), and one of the two values of the fāʾ seems relevant and functional. ; Le fāʾ des systèmes hypothétiques en in de l'arabe classique * Critères de prédiction des valeurs sémantiques de fāʾ Résumé Dans les systèmes hypothétiques arabes apparaît très souvent un fa-entre la protase et l'apodose. Selon la grammaire arabe classique, formée sur un corpus préclassique et pour le seul opérateur in des systèmes hypothétiques, le fāʾ marquerait une rupture ...