This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...oportionate to the value of the person in relation to one’s own happiness.
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To illustrate this on the altruists’ favorite example: the issue of saving a drowning person. If the
person to be saved is a stranger, it is morally proper to save him only when the danger to one’s own life is minimal; when the danger is great, it would be immoral to attempt it: only a lack o
f self-esteem could permit one to value one’s life no higher than that of any random stranger. (And, conversely, if one is drowning, one cannot expect a stranger to risk his life for one’s s...