This text examines the concept of reactibility as an essential condition for the emergence and existence of the world. The author argues that the world is not merely a collection of primordial events, but rather a complex set of their mutual interactions and reactions. It is precisely this capacity of events to react to one another that enables the constitution of the world in its entirety. Hejdánek further develops the idea of a hierarchical structure of events, where interactions at the fundamental level open the space for the emergence of higher-order events. Although these higher events are supported and enabled by primordial events, they are not reducible to them nor are they directly formed by them in the sense of mere composition. The world is thus viewed as a dynamic process of continuous interactions rather than a static set of elementary particles or isolated facts. This approach emphasizes the relational and processual nature of reality, where the key element is the mutual influence and response between individual events, forming the fundamental ontological framework for the author's reflection on the nature of the universe.