“You can use standards of legitimacy both as a sword to persuade others, and as a shield to help you resist pressure to give in arbitrarily. (“I would like to give you a discount, but this price is firm. It is what General Motors paid for the same item last week; here is the bill of sale.”) Just as, by finding relevant precedent and principles a lawyer enhances his or her ability to persuade a judge, so a negotiator can enhance his or her negotiation power by finding precedents, principles, and other external criteria of fairness and by thinking of ways to present them forcefully and tellingly: “I am asking for no more and no less than you are paying others for comparable work.” “We will pay what the house is worth if we can afford it. We are offering what the similar house nearby sold for last month. Unless you can give us a good reason why your house is worth more, our”