This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
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Now in what manner does a human being discover the concept of “ value ”? By what means does he first become aware of the issue of “good or evil” in its simp
lest form? By means of the physical sensations of pleasure or pain. Just as sensations are the first step of the development of a human consciousness in the realm of cognition , so they are its
first step in the realm of evaluation.
The capacity to experience pleasure or pain is innate in a man’s body; it is part of his nature, part of the kind of entity he is. He has n...