Deep Disagreements from the Logico-Pragmatical Point of View: An Analysis of Disagreements Based on Moyal-Sharrock’s Interpretation of Wittgenstein’s On Certainty. Argumentation is central to philosophy. One of its primary functions is to resolve disagreement. Yet, there are cases of disagreement that undercut the conditions of possibility for argumentation themselves: deep disagreements. In his seminal paper, Fogelin (2005) conceived of deep disagreements in Wittgensteinian terms by highlighting their “grammatical” character. Other than normal disagreements, which are located in the space of giving and receiving reasons, deep disagreements are concerned with what enables reasoning in the first place. Hence, they cannot be rationally resolved. Drawing on an interpretation of Moyal-Sharrock’s (2007) account of Wittgensteinian certainties, my logico-grammatical account proposes that deep disagreements pertain to certainties, viz. non-proposional ways of acting in the life-world that are epistemologically basic. Furthermore, the logico-grammatical analysis entails a gradual conception of the transition from normal to deep disagreements by differentiating different types (universal, local, personal, linguistic) and origins (instinctive, acquired) of certainties and specifying which forms of certainty can and cannot be dropped. Also, it allows to identify participating in the human form of life and discursive capabilities as conditions of possibility of disagreements. Consequently, it can specify the turning-point at which disagreement transforms into mere difference. It is at this point that the focus of a dispute switches from the rationality of the discourse to that of the agents of discourse.