O'Brien explains the Party's purpose

O'Brien tells Winston that they have brought him to the Ministry of Love not merely to extract a confession or to punish him, but to cure him. He says the Party is not interested in the overt act, only in the thought. 'We do not merely destroy our enemies, we change them.' He describes how the Inquisition failed because it made martyrs, but the Party will not make that mistake. Winston realizes that O'Brien is not pretending; he genuinely believes what he says. The Party will crush him down to the point from which there is no coming back, and then fill him with itself.