He set to work to exercise himself in crimestop. He presented himself with propositions – ‘the Party says the earth is flat’, ‘the Party says that ice is heavier than water’ – and trained himself in not seeing or not understanding the arguments that contradicted them. It was not easy. It needed great powers of reasoning and improvisation. The arithmetical problems raised, for instance, by such a statement as ‘two and two make five’ were beyond his intellectual grasp. It needed also a sort of athleticism of mind, an ability at one moment to make the most delicate use of logic and at the next to be unconscious of the crudest logical errors. Stupidity was as necessary as intelligence, and as difficult to attain.