"My reluctance to use alien invasion is due to the feeling that we are not likely to be invaded and taken over."

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My reluctance to use alien invasion is due to the feeling that we are not likely to be invaded and taken over. It would seem to me that by the time a race has achieved deep space capability it would have matured to a point where it would have no thought of dominating another intelligent species. Further than this, there should be no economic necessity of its doing so. By the time it was able to go into deep space, it must have arrived at an energy source which would not be based on planetary natural resources.

— Clifford D. Simak