I’m not too knowledgeable about painting, or at least not enough to know if this makes sense, but I found out some paintings from Degas called “[La conversation]” (= The discussion). You could easily find some of these just by googling it, but here’s a page where you can see it for now

By the look of it, it may seem unfinished. And I think that may be the source of this sentence: explaining that painting. Therefore I would translate :

La conversation dans la vie réelle est pleine de phrases à moitié terminées et de discours qui se chevauchent. Pourquoi en serait-il autrement de la peinture ?