This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...ional being are: thinking and productive work.
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If some men do not choose to think, but survive by imitating and repeating, like trained animals, the routine of sounds and motions t
hey learned from others, never making an effort to understand their own work, it still remains true that their survival is made possible only by those who did choose to think and to discover the
motions they are repeating. The survival of such mental parasites depends on blind chance; their unfocused minds are unable to know whom to imitate, whose motions it is safe to follow. They are...