This study deals with the sceptical arguments by one of the most important figures in the philosophical Sufi tradition (the Akbarian school) and the foremost disciple of Ibn ʿArabī, Ṣadr al‐Dīn al‐Qūnawī. Though not a sceptic in the strict sense, Qūnawī employs sceptical arguments from relativity of rational knowledge and disagreement among philosophers to prove inefficacy of reason and rational procedures of knowledge in terms of achieving certain knowledge of metaphysical matters, namely of God and the ultimate principles of things. The paper questions Qūnawī's implicit assumption that, if there is disagreement on a proposition p, then p is relative and thus cannot provide certain knowledge. It aims to philosophically analyse and assess his scepticism as well as to shed light on the largely unknown terrain of scepticism in the mediaeval Islamic world.