This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
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The difference between “standard” and “purpose” in this context is as follows: a “standard” is an abstract principle that serves as a measurement or gauge to guide a man
’s choices in the achievement of a concrete, specific purpose. “That which is required for the survival of man qua man” is an abstract principle that applies to every individual man. The t
ask of applying this principle to a concrete, specific purpose — the purpose of living a life proper to a rational being — belongs to every individual man, and the life he has to live is his...