In 1984, how does O'Brien exhibit doublethink throughout Winston's ordeal?

Winston's torture and "reintegration" at the hands of O'Brien in the depths of Miniluv is the most harrowing passage in 1984. This is not just because of the physical torment that Winston experiences, but also because of the chilling way in which O'Brien demonstrates the power of the Party, power which transcends ideology. He demonstrates the principle of doublethink by first getting Winston to say that Oceania has always been at war with Eastasia,...

Winston's torture and "reintegration" at the hands of O'Brien in the depths of Miniluv is the most harrowing passage in 1984. This is not just because of the physical torment that Winston experiences, but also because of the chilling way in which O'Brien demonstrates the power of the Party, power which transcends ideology. He demonstrates the principle of doublethink by first getting Winston to say that Oceania has always been at war with Eastasia, though Winston previously believed that it had been at war with Eurasia. He tells Winston that he has "created a legend about three men [Jones, Aaronson, and Rutherford] who had been condemned to death for treachery" (257). He tells him that these men never existed, and the piece of paper that Winston saw indicating their innocence was also a fabrication. He even gets Winston to say that he is holding up five fingers, although his thumb is clearly concealed. When Winston asks him if Big Brother exists in the same way he (Winston) exists, O'Brien curtly tells Winston that he does not exist. Later, he even asserts that the earth did not exist before the Party, because the Party invents reality:

When we navigate the ocean, or when we predict an eclipse, we often find it convenient to assume that the earth goes round the sun and that the stars are millions upon millions of kilometers away. But what of it? Do you suppose it is beyond us to produce a dual system of astronomy? The stars can be near or distant, according as we need them. Do you suppose our mathematicians are unequal to that? Have you forgotten doublethink (266)?

Even before he is taken to Room 101, he has begun to embrace the self-contradictory ideas O'Brien has presented him with. He writes that two and two make five in a journal and that freedom is slavery. He comes to the conclusion that "[a]ll happenings are in the mind," the most important precondition for doublethink. Winston earlier wrote in his diary that freedom consisted of the ability to say that "two plus two equals four." The opposite of this freedom is doublethink, as O'Brien clearly demonstrates during Winston's ordeal.