People set within a flat world cannot imagine a third dimension. A prisoner inside a cell made of four lines will remain there forever, never noticing that he could escape by moving perpendicular to the plane, by taking flight, pure and simple, up through the nonexistent wall facing the third dimension. That wall only exists in his mind and in his habits, the habits of right, left, forward, and backward, but not of up or down. Nothing would be easier than to help a prisoner escape, if you have, in comparison to him, an extra dimension: you simply take him between your fingers and lift him up,
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