The fourth chapter of Difference and Repetition is one of the most intricate in Deleuze's entire body of work. In this article, I aim to explore the network of concepts within this chapter through a specific lens: the development of the notion of the problem as a concrete universal. Deleuze shows that difference is key to understanding the articulations of being as becoming and that of sense as effect. In this context, the universal and the singular are deeply intertwined through the formulation of problems. This differential synthesis reveals the objective nature of problems, showing that they constitute genuine structures and shape the diverse ways in which they are actualized.