The Trader Principle

The trader principle is the principle of attaining value from other people through mutually beneficial trade rather than force, fraud, or parasitism. It is the principle that one should consume as much as he earns, no more and no less. People should interact with each other peacefully and for mutual gain.

If a man has something to offer to another man, he should be able to convince the other of this through the use of reason. No force is necessary unless the other cannot be convinced. The trader principle states that man should trade value for value as opposed to force for value or non-value for value. This is based partly on justice, in that people should get what they deserve.

The trader principle applies to the non-material realm as well as the material realm.

Love, friendship, respect, admiration, are the emotional response of one man to the virtues of another, the spiritual payment given in exchange for the personal, selfish pleasure which one man derives from the virtues of another man's character.
Ayn Rand, "The Objectivist Ethics"
One should not love another for their faults, but for their virtues. One should not befriend another because the other needs a friend, but because the other, by virtue of his character, has something to offer. Just as with material objects, one should not devote time and effort and emotional investment into another person unless that person has some kind of value with which to repay. One should only trade value for value.