»Neque quidquam intelligi potest esse sine esse«

»Neque quidquam intelligi potest esse sine esse.« On the necessity of being as an epistemological principle in Meister Eckhart and Nicholas of Kues. The paper analyses the plausibility of the reasoning for the rational necessity of being. The decisive point for the question as to why for Meister Eckhart being alone is necessary, unvarying in itself and self-evident is the conviction that nothing can be thought which is distinct from being, outside of being or without being. Eckhart states this basic philosophical insight repeatedly using the how-question: How could something be knowable as being which is not and cannot be? Nicolas Cusanus concurs with Eckhart’s claim that nothingness is absolutely excluded from being and embraces his strategy of argumentation, including the way it is stated. Cusanus adopts the central principle of Eckhart’s thought that being must be absolutely knowable by founding all multiplicity in unity, that is, in the being of unity, taking recourse in this point to the quomodo-question typical for Eckhart. Cusanus claims to have proved philosophically that being is rationally necessary, that it is a comprehensive, ultimate and incontrovertible certainty: Nothing can be truer and more secure than the presupposition of being, which is indispensable for all thinking.