This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...to the question of why man needs a code of values. So long as that question remained unanswered, no rational, scientific, objective code of ethics could be discovered or defined. The greatest of
all philosophers, Aristotle, did not regard ethics as an exact science; he based his ethical system on observations of what the noble and wise men of his time chose to do, leaving unanswered th
e questions of: why they chose to do it and why he evaluated them as noble and wise.
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Most philosophers took the existence of ethics for granted, as the given, as a historical fact,...