A history of ugliness certainly shares some common characteristics with a history of beauty. First, we can only assume that the tastes of ordinary people corresponded in some way with the tastes of the artists of their day.
If a visitor from space went into a gallery of contemporary art, and if he saw women's faces painted by Picasso and heard onlookers describing them as "beautiful," he might get the mistaken idea that in everyday life the men of our time find female creatures with faces like those painted by Picasso beautiful and desirable.
But our visitor from space might modify his opinion on watching a fashion show or the Miss Universe contest, in which he would witness the celebration of other models of beauty.
Unfortunately, when revisiting times long past, this is what we cannot do -- either in relation to beauty or ugliness -- because all that is left to us of those periods are works of art. We have no theoretical texts to tell us if these artworks were intended to cause aesthetic delight, holy fear or hilarity.
To a Westerner, an African ritual mask might seem hair-raising -- but for a native it might represent a benevolent divinity. Conversely, believers in a non-European religion might be disgusted by the image of Christ scourged, bleeding and humiliated, yet this apparent corporeal ugliness might arouse sympathy and emotion in a Christian.
In the Middle Ages, James of Vitry, in praising the beauty of all the divine works, admitted that "probably the Cyclopes, who have only one eye, are amazed by those who have two of them, just as we marvel both at them and at creatures with three eyes." Centuries later, this was echoed by Voltaire (in his "Philosophical Dictionary"): "Ask a toad what beauty is, true beauty. ... He will tell you that it consists of his mate, with her two fine round eyes protruding from her small head, her broad flat throat, her yellow belly and brown back. ... Ask the devil: He will tell you that beauty is a pair of horns, four claws and a tail."
Attributions of beauty or ugliness are often due not to aesthetic but to sociopolitical criteria. There is a passage in which Karl Marx points out how money may compensate for ugliness: "As money has the property of being able to buy anything, to take possession of all objects, it is therefore the preeminent object worth having. ... The extent of my power is as great as the power of the money I possess. ... What I am and what I can do is therefore not determined by my individuality in the slightest. I am ugly, but I can buy myself the most beautiful of women. Hence I am not ugly, since the effect of ugliness, its discouraging power, is annulled by money."
Can ugliness continue to be defined simply as the opposite of beauty? Can a history of ugliness be seen as the symmetrical foil of a history of beauty?
We ought to use caution in considering the history of ugliness. We also should consider how right the witches were -- if indeed they were right -- when, in the first act of "Macbeth," they cry, "Fair is foul and foul is fair."
Umberto Eco is a semiotician and writer. He is the editor of "On Ugliness," to be published this month by Rizzoli, from which this essay is adapted and the images on these pages are taken.