This is a quote from the book "The ​Virtue Of Selfishness" by Ayn Rand
...ving in a society, instead of on a desert island, does not relieve a man of the responsibility of supporting his own life. The only difference is that he supports his life by trading his product s or services for the products or services of others. And, in this process of trade, a rational man does not seek or desire any more or any less than his own effort can earn. What determines his earnings? The free market, that is: the voluntary choice and judgment of the men who are willing to trade him their effort in return.

When a man trades with others, he is counting...
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