Uṣūlist Anticipations of the Conditional Perfection Problem: Evading Inverse Errors in Dalīl al-Khiṭāb, Mafhūm al-Mukhālafa, and al-Istidlāl bi-l-Ḥaṣr by Dr Walter Edward Young

For centuries, under the rubrics of dalīl al-khiṭāb, mafhūm al-mukhālafa, and al-istidlāl bi-l-ḥaṣr, Muslim legal theorists debated the validity of affirming for what is unspoken the contradictory of the ruling for what is spoken. Put differently, if revelation links a ruling to a specified attribute of a thing, does this entail (linguistically, logically, or in some other way) the opposite ruling for what lacks that attribute? Referring to a common example: Does the Prophet’s assertion that zakāt is due on free-grazing sheep (fī sāʾimat al-ghanam zakāt) entail that zakāt is not due on fodder-fed sheep? Navigating the confluence of linguistic and logical implication, uṣūlist discourse on this issue reached a considerable degree of refinement, and has inspired a number of informative studies in past decades. So far, however, some important linguistic-logical parallels seem to have escaped notice. First is the fact that propositions which link a ruling to a specified attribute may be formally rendered as conditionals, and the inference “If p then q, not-p, therefore not-q” (with a conditional major premise) constitutes the formal fallacy of denying the antecedent (aka the inverse fallacy); whereas the inference “If and only if p then q, not-p, therefore not-q” (with a biconditional major premise) is valid. Second is the fact that in some cases contextual factors dictate that propositions formulated as mere conditionals (if p then q) should be understood as biconditionals (if and only if p then q), thus allowing valid inferences of the inverse (if not-p then not-q). Third, and on top of these older, logical observations, modern pragmaticians have developed a lively discourse around “conditional perfection”: our tendency to hear conditionals as biconditionals (subconsciously “perfecting the conditional”) and thus to accept inferences of the inverse. As is too often the case with modern theorists, however, they have proceeded in evident ignorance of very rich and relevant premodern discourses. This talk therefore aims first to present select definitions, typologies, and controversies of the uṣūlist discourse on dalīl al-khiṭāb, mafhūm al-mukhālafa, and al-istidlāl bi-lḥaṣr, second to understand these with reference to their logical parallels, and third to juxtapose all this with a summary of the modern discourse on conditional perfection, suggesting (as in previous studies) how centuries of refined, premodern Islamic theorising and debate can complement and contribute to the (sometimes re-inventive) efforts of modern theorists.