In 1984, what is the reason why Winston is sent to room 101?
Towards the end of the story, the combination of torture and O'Brien's verbal manipulation of Winston Smith does seem to be paying off, however, crucially O'Brien realises that there is deep within Winston some final level of resistance towards loving Big Brother. It is when O'Brien asks Winston directly what he feels about Big Brother, and receives the response that Winston hates him, that he is taken to Room 101. The reason, as O'Brien explains, is as follows:
Then the time has come for you to take the last step. You must love Big Brother. It is not enough to obey him: you must love him.
This recognises the basis of Big Brother's power and what lies behind the society of this novel: the Party recognises explicitly that they have only "won" if the people they rule over love the figure that is the basis of their oppression. Power is never secure if the source of that power is hated. It is not enough that Winston is only outwardly compliant and obedient; in order for his rehabilitation to be a success he must be inwardly obedient as well. Room 101 is therefore the ultimate, last form of torture the Party uses in order to make people love Big Brother against their better wishes.