“Not merely the validity of experience, but the very existence of external reality, was tacitly denied by their philosophy. The heresy of heresies was common sense. And what was terrifying was not that they would kill you for thinking otherwise, but that they might be right. For, after all, how do we know that two and two make four? Or that the force of gravity works? Or that the past is unchangeable? If both the past and the external world exist only in the mind, and if the mind itself is controllable what then?
But no! His courage seemed suddenly to stiffen of its own accord. The face of O'Brien, not called up by any obvious association, had floated into his mind. He knew, with more certainty thanbefore, that O'Brien was on his side.”