CHAPTER XV
√-1
When you come to quadratic equations you will be confronted with an entity (or non-entity) whose name is written this way—√-1, and pronounced "square root of minus one." Many people let this nonentity persuade them to foolish courses. A story is told of a man at Cambridge who was expected to be Senior Wrangler; but he got thinking about the square root of minus one as if it were a reality, till he lost his sleep and dreamed that he was the square root of minus one and could not extract himself; and he became so ill that he could not go to his examination at all. Angels, and square roots of negative quantities, and the other things that have no existence in three dimensions, do not come to us to gossip about themselves; or the place they came from; or where they are going to; or where we are going to in the far future. They are messengers from the As-Yet-Unknown; and come to tell us
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