Deleuze begins this series with the statement that "Events make language possible." This describes, in a general way, the subject for the rest of the book. This series marks a dividing line or a major inflection point in The Logic of Sense as he shifts his focus to psychoanalysis in the next series and stays with it until the Appendices.
Deleuze performs his philosophy with the form of the book. In the previous series on Univocity, he said the problem has shifted to how does the individual transcend their form and syntactical link to a world. He also discussed the Eternal Return in the previous two series. After suggesting the individual transcend their syntactical link, he returns to language, and spends the remainder of the book writing about how this syntactical link gets formed. This first part of this series recapitulates and reiterates material from Series Two, Three and Four, another kind of Return. After this review, Series Twenty-Six explicitly returns to looking at what makes language possible. This series also appears isomorphic with the incorporeal line-frontier that separates bodies from propositions. It separates the first twenty-five series, primarily of philosophy (concepts and ideas), from the remaining eight series concerning the "dynamic genesis," the development of the human body from birth into what Jaques Lacan calls the Symbolic Order, i.e. incorporating language into their world. Events and sense get used interchangeably. Deleuze explicitly states their equivalence. It's equally correct to say that sense makes language possible. The verb constitutes the ring of the proposition bringing signification to bear upon denotation. A verb has two poles that it oscillates between: the infinitive which indicates the sense or event, and the present which indicates its relation to a state of affairs. It is from the verb that we infer what the ring conceals or coils up or what it reveals once it is split, unrolled or deployed over a straight line - sense or the event as the expressed of the proposition.