In the end the party would announce the two and two made five and you would have to believe it, was inevitable that they should make that claim sooner or later the logic of their position demanded it! Not merely the validity of experience, but the very existence of external reality was denied by their philosophy. The heresy of heresies was common sense. And what was terrifying was, not that they could kill you, but that they might be right! For after all, how do we know that two and two makes four, or that the force of gravity works, or that the past is unchangeable? If the past and the external world exists only in the mind and the mind is controllable, what then