A dog will pursue rabbits to the point of complete exhaustion and be happy all the time, but if you put the dog on a treadmill and gave him a good dinner after half an hour, he would not be happy till he got the dinner, because he would not have been engaged in a natural activity meanwhile. One of the difficulties of our time is that, in a complex modern society, few of the things that have to be done have the naturalness of hunting.
Source: Bertrand Russell: The road to happiness (1952)
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