This article examines Ibn Taymiyyah’s view of certainties and the premises of demonstration in his book, al-Radd ʿalā al-Manṭiqiyyīn. Employing a library-based method and an analytical–inferential approach, the study seeks to evaluate Ibn Taymiyyah’s assessment of the premises of argument and demonstration, with particular emphasis on the status of certainties and their referents. Ibn Taymiyyah maintains that Aristotelian–Avicennian logic, while preserving its formal framework, ought to include prophetic reports and the reports of the infallibles —according to his view — among the certainties; since it fails to do so, its classification of certainties remains incomplete. The most prominent class of certainties, namely first principles (awwaliyyāt), also possesses a general content whose universality bears no link and relation to the real world. Finally, he claims that primary self-evident propositions hold no priority over widely transmitted reports (mutawātirāt) and empirical premises (mujarrabāt) in demonstrative reasoning and these two groups share with first principles the features of general accessibility and universally comprehensible. In order to analyze these three claims, this article is structured in three sections, evaluating Ibn Taymiyyah’s position in each section. The study concludes that none of these claims can be adequately established and that each is open to refutation.