Sometime around 1515, the Venetian artist Titian painted a scene usually titled “Sacred and Profane Love.” In it, two women are seated at a marble well; one is nude, the other elaborately dressed. It comes as a shock to many Americans to find out that in this allegory, sacred love is represented by the naked lady.

And in general, Americans seem to have a difficult time with the nude in art. Maybe it is America’s Puritan heritage, maybe it is the low priority given art education in our schools.

Sometimes it’s just pig ignorance.

But to many Americans, the nude is something dirty, lewd and embarrassing. At the very least, nudity is equated with sexuality and eroticism.

As they said on “Seinfeld,” “Not that there’s anything wrong with that.”

We can laugh at the silliness of such a view, but it governs much of what Americans think about sexual morality, including former U.S. Attorney General John Ashcroft, who spent $8,000 in 2002 on blue drapes to hide two giant Art Deco statues — “The Spirit of Justice” and “The Majesty of Law” — at the Great Hall of the Department of Justice in Washington.

Certainly, there is a good deal of eros in art history.

Take for instance, Francois Boucher’s “Reclining Nude” from the French 18th century.

There is not much about this luscious painting that is different from, say a photograph with a staple in the middle.

An in America, too often, this is all that a nude is.

A few years ago, a woman in Tucson demanded that art and art books be removed from a public school, calling works by established masters ”pornographic and morbid.”

She was talking about Michelangelo’s “David” and Picasso’s  “Demoiselles d’Avignon.”

What is more astounding is that she managed, at least temporarily, to have 10 art books and four posters yanked from the school. The works in question were by Edouard Manet, Frida Kahlo, Paul Gauguin, Hieronymus Bosch and El Greco.

She said she considered El Greco a ”pervert.”

”We left the art teacher with about five books,” she said, with some pride. ”I took out anything with nudity in it. There’s no difference between a nude (in an art book) and a ‘Playboy’ picture.”

I’m not interested so much in the question of what is appropriate for fifth- and sixth-graders; there may be some legitimate concern for their sensibilities. Although, in this case, I doubt the kids are getting anything from Gauguin they haven’t learned long ago from Aaron Spelling.

But, I am very much interested in the widespread belief that nudes are necessarily pornographic.

Such a view ignores the evidence of centuries of art that has portrayed the human body for other, more complex purposes.

Varieties of nudity 

So what are those purposes? In other words, what does the nude mean?

All but a few cultures in the history of the world have had a place in their art for the undressed human body. Although it is probably more developed in European art than elsewhere, the nude body appears prominently in African, Persian, Hindu, Tibetan and Japanese arts.

It occurs with different meanings in them: In Chinese art, the nude is rare; the most frequent nudes are not sleek ideals of human form but fat Buddhist monks, looking like the sileni of Greek art.

But you will see that these are not different merely in style, but in purpose: These are all different meanings for the nude and the human form.

Of course, in the geography in which humans evolved, there was less need of heat-conserving hair. And in those climes, nudity has different cultural meanings.

And titillation is rarely the primary factor involved.

Like the prisoners in Abu Ghraib — Surely being made to exhibit themselves naked means more to them than it would to us, even if we feel humiliation in our nudity, how much worse is it for these Arab men?

In the temple art of India, nudity and copulation are used as a metaphor for the Cosmos. There is not one single meaning for the nude, but rather a series of layers of meaning that can overlap. Those layers run from the most primitive to the most sophisticated. There are at least four distinct layers of meaning to be addressed:

–> Appetite;

–> Intellect;

–> Power;

–> and Spirituality.

The first layer is really that of plumbing.   At the level of appetite, we have the gaze of the voyeur.

It is here we find everything from men’s room drawings to “Debbie Does Dallas” to the pillow books created by Japanese artists in the 18th century.

The faces mean little, the beauty or fitness of the physiques mean little. There is nothing going on but what Joseph Campbell has called the ”zeal of the organs for each other.”

All true pornography stops at this basement level.

And it is this level that most of the moralizing critics of the nude are stuck in, unable to see any higher.

The rippling of silk 

The second layer is that of both eroticism and idealization.

In both cases, the mind takes over from the organs and imposes standards.

Eroticism is the level at which the rippling of a silk dress is more arousing than raw flesh, with all its hair, bruises and cellulite. Pornography is stunningly literal-minded; eroticism is imaginative.

And eroticism’s flip side is the idealized nude of ancient Greece or “Playboy” centerfolds. In each case, an ideal form is held in the mind – an ideal the real world cannot actually live up to; hence the canon of Polyclitus, which defined the proportions of the perfect body, and the airbrush of Hugh Hefner.

When Sir Kenneth Clark wrote his famous book about the nude, he focused almost exclusively on this aspect of the figure in Western art: The idealization of beauty.

Here we find the pneumatic Boucher cuties and the massive Classic Zeus in bronze throwing his thunderbolt.

If pornography is often physically repulsive, no matter how fascinating, the idealized nude is  intended to be attractive. The idea of beauty enters into the equation.

The so-called Venus of Willendorf, from at least 24,000 years ago, found in what is now Austria. Is this an ideal of beauty? It is certainly an image of fertility. And fertility and beauty are often the same thing, when you live in a time and place that survival depends on fertility.

In Ancient Greece, where we generally start our narrative of Western art, the earliest statues were an expression of human perfection. And for the Greeks, human perfection meant the male human form. They worshipped male beauty. Greek vases are full of nude male bodies — athletes in the Panathanaic Games, for instance.

The early kouros was still rather stiff, by modern standards, but compared to what went before, in Egypt or Babylonia, it is a model of realism and accurate observation.

I don’t want to make this a chronological history. You have schools for that.

But you are familiar with lots of nudes in European art from the Renaissance to now.

Rather, I want to look at some thematic ideas, how the nude changes meaning.

The body still remains, however, essentially an object rather than a person.

How the world works 

We’ve seen the erotic nude, but that’s not all there is.

A third level, above the erotic and the idealized, is the level of power and the political, psychological and scientific.

What does the nakedness here tell us? It tells us these people are powerless, humiliated, tortured and suffering.

There is a famous picture by Imogen Cunningham of a young woman with her head and hair hanging off the edge of a bed. It is erotic.

But put it beside this and you see the similar pose with a completely different meaning.

No one who has seen pictures of naked Jews herded into the showers of Auschwitz can fail to recognize the political significance of nakedness. It functions to underline the powerlessness of the victims and their vulnerability.

Context makes a huge difference.

And in Manet’s famous painting, “Dejeuner sur l’herbe,” the message that comes through is ostensibly erotic, but in reality is political: Two fully clothed middle-class men are having a picnic with two nude women.

The ridiculousness of the scene makes fun of the traditional power relationship between men and women. The painting pointedly comments on such earlier paintings as Georgione’s “Fete Champetre,”   in which two Renaissance courtiers talk animatedly with each other while attended by two docile and idealized nude women.

And it comments on such popular paintings of Manet’s time as Gerome’s “Slave Market,” in which clothed men paw over a nude woman, checking her teeth before purchasing her.

Gerome’s painting is merely a salacious bit of kitsch; Manet’s is biting and political. (One shouldn’t discount the tacit political message in the Gerome, probably unnoticed by the painter: Who has the power here? It isn’t the woman.)

It’s no wonder that “Dejeuner” was declared indecent while such paintings as the “Slave Market” made Gerome a wealthy man: By making his figures  bourgeois, Manet was pointing a finger at his audience. It is political commentary.

Many left-wing feminist critics of the nude get just as stuck in this level as their Christian right-wing counterparts get stuck in the first.

But the power I’m talking about at this level isn’t only political power. It is the power of  humankind over itself and the power to understand the world it lives in.

For instance: If Renaissance artists hadn’t become obsessed with drawing the nude figure, modern life expectancy would likely still be short and brutal. Modern medicine could not have developed without such artists as Leonardo and Michelangelo taking an interest in how the human body looks and how it is put together.

Before the Renaissance, Gothic artists created the figures they used to decorate the cathedrals from their imagined forms. If a figure had a torso, two legs, two arms and a head, it was enough. The bones, muscles, tendons and sinews that lay underneath the surface might as well not have existed.

”It seems rather as if you were looking at a sack of nuts than a human form, or at a bundle of radishes rather than the muscles of nudes,” wrote Leonardo of unobservant figure drawing.

But the Renaissance brought with it an interest in how the world works, how the parts of the body work.

Those artists studied the world around them intently. And to them, the most interesting thing in the universe was humankind. The human figure was to them the most perfect and beautiful form found below the level of the angels.

”Who is so barbarous as not to understand that the foot of a man is nobler than his shoe, and his skin nobler than that of the sheep with which he is clothed?” wrote Michelangelo.

In other words, clothes are trivial, the naked human body, essential.

But even at this level, so much more profound and moving, the figures still represent ideas and are not fully humanized, not fully individualized.

Empathetic encounters  

At its highest level, the nude represents spiritual virtues, unencumbered by fashion. The nude is universally true. That is why Titian’s sacred love must not wear the silks and finery of her earthly sister.

Angels are nude, and so are the putti, or cherubs, that flit around so many Baroque allegories.

Michelangelo’s designs for the Sistine Chapel are monumental nudes for that reason, and for another:

When art is most profound, it draws us out of  ourselves and forces us into an empathetic encounter with things and people who are radically different from us.

It is not possible to view the figures of the Sistine Chapel with any intensity and not feel your own body compared with them. Their sinews are your sinews; their contorted muscles are yours.

It is why the nude is used for the most profound tragedies in art: the nude Pieta and the Crucifixion, to name two very Christian uses of the nude.

Angels are often drawn as putti, or cupids, in part for their association with innocence.

We look at one of Matthias Grunewald’s tortured crucifixions and cannot help but feel the pain in our own flesh.

In all the greatest art, we are thus drawn out of ourselves and identify with the grace, power, suffering and love of others and come to escape   the isolation — and loneliness — of the ego. We recognize the similarities of all humanity and not its petty differences.

Whatever it means in religious dogma, the Christ is symbolic of our own mortality.

A lot of wind has been spent on the argument over whether there are any universal truths in the world. So many of the old Truths now seem mendacious. But there are two truths that are inescapable. We die, and people we love die. Loss is central to the human experience. It is why Michelangelo’s “Pieta” is meaningful, even for the atheist.

Our recognition of our humanity is one of the highest aims art can attempt.

It is why Rembrandt’s nude portraits of his two wives are so compelling, why Goya’s “Disasters of War” are so frightening.

And not only are the figures in the art thus humanized, but the viewers are as well.