1984 Section One, Part VII Analysis (pp. 69-81)
Winston places hope in the proletariat, the working class, because they have not been dehumanized by Big Brother nearly to the extent Party members have. The "proles" are still capable of generating the raw emotion needed to overthrow the Party. However, they are largely uneducated, and thus unaware. This trait allows them to be easily controlled by the Thought Police.
While thinking about the "proles", Winston's ulcer starts itching. Winston is disturbed by his thoughts and he is repressed in ways the proletariat is not. His ulcer is both a symbol and expression of this repression.
The discussion of the picture Winston found is important to the novel. Winston will undergo the very same process as Jones, Aaronson, and Rutherford, which signals the reader what will happen to Winston after the novel ends: he will be executed. He will even hear the same song Jones, Aaronson, and Rutherford had heard in the café. The picture itself is important because it a palpable piece of the past. Because he could physically hold it, his perception of reality is altered such to believe the past is immutable. Without it, he has only his mind to rely on to prove existence of the past, and the past then becomes mutable. O'Brien will later torture Wilson to the point of believing the picture does not exist, that it never existed.
In this section Winston realizes he's writing the diary to O'Brien. This is more true than he knows because, as the reader later learns, O'Brien is probably reading what Winston writes soon after he writes it. Winston is right to believe he has some kind of connection to O'Brien, but he doesn't know O'Brien is setting him up. Winston wants to hold on to the idea that physical laws don't change and that two plus two will always equal four. O'Brien, however, will torture him until he believes otherwise and that two plus two equal whatever the Party says they equal.