This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...f into a subhuman creature and he can turn his life into a brief span of agony — just as his body can exist for a while in the process of disintegration by disease. But he cannot succeed, as a
subhuman, in achieving anything but the subhuman — as the ugly horror of the antirational periods of mankind’s history can demonstrate. Man has to be man by choice — and it is the task of
ethics to teach him how to live like man.
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The Objectivist ethics holds man’s life as the standard of value — and his own life as the ethical purpose of every individual man. <...