The discussion centers on proving that if F is a monotone function and C is the union of sets invariant under F, then F(C) equals C. A participant questions the correctness of their proof, specifically regarding the relationship between elements of C and subsets X of A. They express uncertainty about why an element B in C implies the existence of a corresponding subset X such that X is a subset of F(X). The conversation highlights the need for clarity in establishing this connection within the proof. The thread ultimately seeks to validate the proof's logic and completeness.
