During Winston's interrogation, O'Brien insists that there is no external, independent reality, that the only reality is inside one's own mind. This is part of a philosophical tradition called solipsism, which O'Brien refers to, but he takes it one very important step further.He explains that as the Party aims to completely control the minds of individuals, this effectively means that reality is wherever the Party decrees it to be.This is manipulation to an utterly frightening, and potentially limitless extent.The Party wants individuals not merely to accept what it says is real, or right, but to literally believe it. Winston puts up a struggle against this for a time, even during his interrogation and torture, but ultimately, he cannot prevail.
Like a good Nietzschean, O'Brien believes that power creates reality. Those in power (or as O'Brien terms it, "control") determine truth. O'Brien says to Winston:
‘We control matter because we control the mind. Reality is inside the skull. You will learn by degrees, Winston. There is nothing that we could not do. Invisibility, levitation—anything. I could float off this floor like a soap bubble if I wish to. I do not wish to, because the Party does not wish it. You must get rid of those nineteenth-century ideas about the laws of Nature. We make the laws of Nature.’
Reality is in the hands of the Party. There is no external reality. Reality is whatever the Party (the ultimate power in Oceania) says it is, according to O'Brien.
"Nothing exists except through human consciousness," says O'Brien.
Winston stubbornly maintains that there is an external reality, independent of human consciousness and Party control, an objective truth that exists regardless of human thought. For Winston, at least until he is broken, two plus two equals four regardless of what the Party says. He struggles for the word to describe O'Brien's assertions about reality. O'Brien supplies it: Solipsism, the idea that only what is in the mind exists. But O'Brien insists that what he asserts is not solipsism:
The word you [Winston] are trying to think of is solipsism. But you are mistaken. This is not solipsism.
O'Brien then returns to power: reality is not solipsism but power, and power is the boot stamping the human face. Power tells people what is real and people are forced to accept it. This acceptance, to satisfy the Party, must not be simply external assent but internalized belief.