Winston again dreams of the Golden Country, his nostalgic place where everything is peaceful. Ironically, he dreams of O'Brien being there; his torturer has become his only friend, an example of doublethink, being able to hold two opposing ideas at the same time and believe absolutely in them both.
Like every person, Winston has a breaking point, and O'Brien has found it: rats. The seemingly unimportant scene earlier in the story where Winston becomes terrified of the rats in Mr. Charrington's upstairs room betrayed his phobia. The Party indeed knows everything about its constituents, including how to get inside their minds — something that Julia and Winston did not believe possible.
The fact that Winston betrays Julia is the ultimate irony; the Party has succeeded in making the couple stop loving each other, effectively destroying the only thing that they believed made them human. Remaining human was Winston's only goal, to keep the few centimeters within his head his own; however, the Party does own everything and only for the sake of owning it.
Winston betrays Julia to save himself, a human act of self-preservation, even though the self is supposed to be reserved for the use of the Party. By saving himself, Winston commits a selfish act, and thus should be punished for it; however, he is spared. This can be seen as a flaw in the story.
