Moral overload and moral dissonance

Suppose you are far away from home, traveling alone on a highway. You stop at a busy roadside restaurant for dinner. The food is decent and the service acceptable. When the bill of $13.64 arrives, an inner voice tells you that the waitress deserves the customary 15 percent tip. Reaching into your pocket, you notice that you are carrying only bills in the amounts of $5, $10, and $50. Through a quick mental calculation, you realize that a payment of $15 would leave the waitress a smaller tip than what you consider fair. Alas, being in a hurry to reach your hotel, you would rather not wait for the change on $50. Following a moment's hesitation, you drop $15 on the table and head for your car. The decision is now behind you, but not the issue. For a while, until a melody on the radio carries your thoughts elsewhere, you feel a bit guilty for having been unfair to the waitress for the sake of a little extra sleep.

You were a complete stranger in the restaurant, and you probably will not see the waitress again. What has given you trouble is not, therefore, the possibility of social sanctions. It is, rather, your conscience. Your choice failed to accommodate a value that you hold – the principle that people should receive their due. Not satisfied with the preference that your choice revealed, you feel that you ought to have behaved differently.