The theme of dystopian society makes Orwell's novel one of the most powerful in English Literature. It is particularly through Winston's torture at the hands of the charismatic O'Brien that the reader is able to see a leadership so convinced of its right to power that it believes it can alter the the most basic premises of human logic and instincts. However, the Party knows that driving all its repressive measures there needs to be a central figure of 'truth' and authority that the people can be coaxed into adoring.
Big Brother represents the deification of authority that the Party needs to maintain its iron grip over its citizenry. Whether Big Brother actually exists is not made clear, but this serves to reinforce the point that it is simply the credible perception of an all powerful leader supposedly benevolently acting in the citizenry's best interests that facilitates blind following. In the novel it enables the Party to dispense all-manner of propaganda and rob the people of even their most intimate privacy and freedoms; all under the guise of acting in the greater interests of the people as determined by the diefied Big Brother. Winston, the intrepid protagonist who had dreamed of undermining the state, eventually becomes the embodiment of the ultimate victim of a dystopian society - a hapless, brainwashed shell of a human,
"He gazed up at the enormous face. Forty years it had taken him to learn what kind of smile was hidden beneath the dark moustache....But it was alright, everything was all right, the struggle was finished. He had won the victory over himself. He loved Big Brother" (p. 311).