We might urge people to do unto others, etc., or, per Kant, to act only in accord with a principle that they would at the same time will to be universal law, but we should be clear that behaving in such a manner is more likely to encourage others to behave otherwise—to act more selfishly. This is not to say there aren’t some people who, for instance, if you are courteous to them, will be more inclined to be courteous to you—and many more will enjoy saying thank you. But there are certainly those—to include many who earn their living on the island of Manhattan—who, seeing you behave in such an obliging fashion, may take you for a fool or an unambitious no-account, and in any case will take advantage of your courteousness, generosity, understanding, et al., as it suits their needs or whims.
This is not to say that one should never be courteous, for instance. One might be courteous simply for the pleasure being courteous brings—although one should keep in mind that this pleasure has a great deal to do with two extravagant fantasies. The first is that acting courteously promotes courtesy, that it promotes a “better”—i.e., more orderly, well-mannered—world. The second is that acting courteously shows the fundamental goodness of one’s nature. As Kant pointed out, the person who finds pleasure or other reward in behaving in an exemplary manner—who, for example, acts honorably because he wishes to be honored—“deserves praise and encouragement, but not esteem,” self-interest being at the source of his behavior.
One might also be courteous where it produces more practical positive reactions. For example, one might be courteous with those people who do respond courteously to courtesy, or with people, such as a boss, who will take such behavior as a sign of deference and who will rarely be disturbed to find underlings appearing inferior.
It should also be noted that, insofar as the recipient of one’s courtesy has not asked for it, he may, and often with good reason, resent or be suspicious of it, wondering what may be requested in return. He may feel he has been committed to a deal without having had the chance to even review the terms. The recipient may sense the courteous person fancying that—not that he would ever mention it, of course, but in fact—he is entitled to something, to his “thank you” at the very least. And sensing as well the pleasure that this person has taken in his “courteous” gesture, the recipient may wish for rather more recognition of the essential contribution that he, the recipient, is making to this other’s person’s happiness.