A few years ago, I saw an exhibition at the Met Breuer Museum in New York about unfinished art.

The show included work from the Renaissance through the 21st century.

And it really moved me, like so much that I bought the hulking book that accompanied the show.

I mean, you could do bicep curls with this thing and get reasonably fit.

But when I look at a painting like The Virgin and Child with Saint John and the Angels, I'm reminded first that art is made by people.

We don't know why this was left unfinished.

It may have been that a patron flaked or that a more interesting opportunity arose.

Artists are not like geniuses, who are fundamentally different from us, but human beings who live in time and space.

Like any of us, great artists are both making history and being subjected to it.

Like us.

they fail to finish things because they get bored, or because they discover a problem they can't figure a way around, or because they received word that a loved one is sick and they must abandon work to care for them.

Still, there can be so much wonder and beauty to unfinished art.

The figures to our left are just coming into being, almost sculptural in their outline.

In the center of the picture, Mary is trying to hold a book away from the baby Jesus, which 16th century viewers would have known to be part of the book of Isaiah that foretells of a messiah pierced for our transgressions and crushed for our iniquities.

Even when your kid is the Son of God, I guess you still want to protect him from suffering.

Other times the historical significance of an artwork is not so much the work itself as its context.

Like in the United States, we have a tradition of the official presidential portrait.

And with the major exception of Kehinde Wiley's portrait of President Obama, most of these portraits are, I'll put this charitably, competent but uninteresting.

It's like "I'm touching papers.

"I'm also touching papers.

"I prefer holding my paper, as do I. I'm touching papers while holding my place in a book," and so on.

Anyway, Franklin Delano Roosevelt's official presidential portrait is exactly as you'd expect.

It's, you know, competent.

But by far my favorite painting of FDR is this unfinished watercolor painted by the Russian-American artist Elizabeth Shoumatoff in April of 1945.

FDR was seated at a card table.

And Shoumatoff had only been painting for a little while when the president said, "I have a terrific pain in my head," and collapsed.

He died later that afternoon.

Shoumatoff never completed the painting.

But she did later make a finished portrait based from memory.

And in that finished portrait, of course, the president is holding paper.

Both portraits romanticize a frail old man.

I mean, the day before Roosevelt looked like this in a photograph.

But to me anyway, Shoumatoff's unfinished portrait is more arresting and powerful than her completed one.

It's a fierce and riveting reminder that, to quote the last words of another U.S. president, "We are all going."

The unfinished painting's power is partly in its historical context, of course.

I mean, if the artist had quit at this moment because she had a hand cramp, the picture wouldn't mean as much.

But then all art is context dependent.

Really, all everything is context dependent.

In a similar vein, I love Benjamin West's unfinished painting Treaty of Paris, which was supposed to commemorate the treaty ending the U.S.

Revolutionary War.

Leaders of the American independence movement, including Benjamin Franklin, are depicted here.

But the British delegation refused to pose for a picture commemorating their defeat.

Other times work goes unfinished because the artist dies.

Such was the case with Laura Knight's unfinished portrait of Vijayalakshmi Pandit, former president of the UN General Assembly, or this Gustaf Klimt painting called The Bride, which was left incomplete when Klimt died in 1918 as a result of a global flu pandemic.

And then there is the gut-wrenching story behind Ford Maddox Brown's painting, Take Your Son, Sir!, which showed his wife Emma holding their newborn son Arthur.

Brown abandoned the painting in 1857 when Arthur died at just 10 months old.

In this way, an unfinished painting can be a kind of memorial to an unfinished life.

When I look at this painting, I'm reminded of Kafka's novel The Castle, which was left unfinished when Kafka died at 40 of tuberculosis.

The Castle ends, "She spoke with great difficulty, it was difficult to understand her, but what she said," and that's the end.

We'll never know what she said, just as we'll never know what Arthur's life might have been.

Unfinished paintings can also be important to curators and conservators trying to understand art history.

Like, take, for, example this Perino de Vaga painting of The Holy Family with Saint John the Baptist.

You can see the map the artist laid out, known as underdrawing, and in doing so glimpse some of the techniques used to construct perspective and facial features.

As Met curator Kelly Baum put it, "An unfinished painting is almost like an X-ray, "which allows you to see beyond the surface of the painting "to what lies behind-- "earlier versions, preparatory sketches, "all the underlying architecture which is normally disguised and suppressed."

In that sense, unfinished paintings can become a kind of archaeology.

Like almost 2,00 years ago, Pliny the Elder wrote in his Natural History, "The last works "of artists and their unfinished pictures "are more admired than those which they finished, "because in them are seen the preliminary drawings left visible and the artists' actual thoughts."

And then, of course, unfinishedness can also be an artistic choice, as it is in this portrait by Kerry James Marshall, where there is no black in the artist's palette and the paint-by-numbers work in the background remains unfinished.

The tradition of intentionally not finishing something, sometimes known in art history circles as the non finito, is widespread in art history.

The art historian Carmen Baumbach has argued, for instance, that this astonishing portrait was considered complete, if unfinished, by Leonardo da Vinci.

And this gets at a complex question in art and in life-- Does something have to look finished to be complete?

My favorite art work that explores that question is Alice Neel's James Hunter Black Draftee from 1965.

Neel met James Hunter less than a week before he was scheduled to fight in Vietnam after being conscripted into the U.S. Army.

Hunter only showed up for one sitting with Neel, who eventually decided to sign the painting and declare it complete.

You can feel the worry and the weight of being forced into a war, not just in the detailed face of the portrait, but also in its sketched lines.

And while Neel's finished paintings often shimmer with emotional ferocity, this painting is especially haunting because of its incomplete finishedness.

And this goes way back in art history.

Like in the Renaissance, several artists employed the so-called Plinian signature, wherein they would use the Latin word "faciebat" when signing their work.

Roughly translated, instead of saying in Latin "this sculpture was made by me," they would sign, "this sculpture was being made by me," implying a permanent unfinished about it.

In fact, the only time Michelangelo ever signed a work, The Pieta, he used that imperfect tense.

The Pieta, of course, looks very, very finished.

The crucified Jesus being held by his mother is so finely wrought that you can see his ribs visible beneath his skin.

The gaunt, exposed Christ is starkly contrasted with Mary's flowing, billowing robes.

The abundance of life is holding the emaciation of death.

It's a hell of a sculpture.

But so are these four famous unfinished sculptures also attributed to Michelangelo.

The Pieta is made from marble.

But these figures seem to be encased in marble, almost as if they are trying to emerge from it.

In these sculptures, known as Prisoners or Slaves, chisel and mallet marks are still evident.

Michelangelo's friend Giorgio Vasari wrote that "the figures are emerging from the marble as though surfacing from a pool of water."

You can feel how hard it is to make a sculpture.

But you can also feel how hard it is to be a person, especially in this sculpture commonly called Atlas, because the headless figure is carrying so much weight.

I mean, who among us hasn't on occasion felt a bit Atlasy?

Michelangelo famously once wrote that "Beauty is the purgation of superfluities."

The perfectly polished, breath-stealing-rich Pieta has been purged of all that is superfluous, but so I would argue have the Prisoners or Slaves.

Just enough of the marble is gone for us to feel the humanity of these sculptures, a reminder that art need not be finished to be meaningful.

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