This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...de, from its physical background, and the action of its own body, the action of using that fuel properly. What standard determines what is proper in this context? The standard is the organism’
s life, or: that which is required for the organism’s survival.
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No choice is open to an organism in this issue: that which is required for its survival is determined by its natur
e, by the kind of entity it is. Many variations, many forms of adaptation to its background are possible to an organism, including the possibility of existing for a while in a crippled, disabled...