One mornining a man is walking along a beach after a storm.  Thousands of sea stars washed up on the sand and will die in the sun.

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He notices a child picking up the sea stars one by one and throwing them back into the ocean.

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The man says, there are thousands of starfish here.  You can't possibly make a difference

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The child picks up another sea star, throws it into the water and says: It made a difference to that one