 Thirdly, incompleteness may be irresolvable. The most natural reason for this is that the alternatives differ in terms of advantages or disadvantages that we are unable to put on the same footing. A person may be unable to say which she prefers—the death of two specified acquaintances or the death of a specified friend. She may also be unable to say whether she prefers the destruction of the pyramids in Giza or the extinction of the giant panda. In environmental economics, as a third example, it is a controversial issue whether and to what extent environmental damage is comparable to monetary loss.