Anyone visiting the Pennsylvania Academy of the Fine Arts hoping to see both of its Edward Hopper paintings will be disappointed. The academy sold Hopper's East Wind Over Weehawken (1934) in December for $40.5 million to raise funds for other art. Only his Apartment Houses (1923) remains.

A trip to St. Charles Borromeo Seminary on City Avenue to view its six Thomas Eakins oils will also disappoint. In March, the seminary announced the portraits will be sold to fund renovations. They are no longer on view.

In Wilmington, the Delaware Art Museum has announced it will sell art to raise $30 million for debt service and endowment funding. A jewel of the collection, William Holman Hunt's Isabella and the Pot of Basil (1868), will be auctioned in London next month. Although officials would not confirm it is for sale, Winslow Homer's Milking Time (1875) has been taken down.

In each of these cases, a visitor would learn one thing above all else: Artworks are commodities bobbing in a huge and ravenous art market.

But are they something more?

When a work is sold, other art can be purchased (or not), operating funds raised, capital projects funded. But such sales raise difficult questions, not the least being whether a work of art has value not measurable in dollars. When an artwork vanishes from the public landscape, what is lost?

For one thing, says Michael Lewis, professor of art history at Williams College and a Philadelphia resident, key artworks become emblematic of a place and a time, fusing with their surroundings.

"Certain things are more valuable in certain places," he said.

For instance, the Eakins portraits reflect of the seminary's own history, the regional history of the Catholic Church, and Eakins' personality, habits, and relationships with his powerful, learned subjects.

They include portraits of seminary faculty members, the first Philadelphia archbishop, and a prominent layman. Eakins met most of these men about 1900 after Sunday bicycle rides through Fairmount Park that ended at the seminary. Eakins and his friend, sculptor Samuel Murray, attended vespers, stayed for supper, and talked into the night.

An earlier subject was Archbishop James Frederick Wood, overseer of seminary construction, who was introduced to Eakins by surgeon and teacher Samuel Gross, subject of The Gross Clinic (1875).

These portraits speak to the world of Philadelphia achievement at its apex and show how intimate that world could be.

Such paintings, in Lewis' view, have a far different meaning elsewhere, and their sale, for whatever reason, is akin to "unpacking a fruit basket and tossing the contents in different directions. You lose something immediately."

Such losses of the "intangibles" intrinsic in a work may seem a bit precious in the 21st-century world of fungible commodities and relativism. And museums and seminaries are frail stewards when set against the muscular art market - global art sales came to $66 billion in 2013, according to a new report from Arts Economics. In the hot glare of all those dollars, the values of identity and place, history and preservation, can easily wither.

The code of ethics of the American Association of Museum Directors, which deplores all museum sales except those undertaken to acquire art, does not specifically address the importance of art to place, and is irrelevant to institutions such as the seminary.

Derek Gillman, former head of the Barnes Foundation and now a visiting professor at Drexel University, says St. Charles Borromeo is within its rights in selling its paintings because "it was not formed as a collecting institution."

He acknowledges that "you can make the argument that the paintings belong to the history of the institution and have a value reflective of that."

But the code of ethics is indifferent to such arguments; the St. Charles sale is "fair," Gillman said. Not fair are the sales by the Delaware Art Museum, a collecting institution that won't acquire art with the money it raises.

"They've broken the rules," Gillman said. "Their issue is, 'OK, we accept that there will be costs to the museum.' "

Gerald Silk, professor of modern and contemporary art and chair of the art history department at Temple's Tyler School of Art, said there's a reason the museum-directors association deplores art sales "for capital expenses or for anything other than . . . acquiring other art."

"You go down a slippery slope. You sell to pay capital expenses. You say this will be the only time. But what's going to happen five years down the road?"

(Why the "slippery slope" argument doesn't apply to institutional sales undertaken to acquire art is not addressed by the museum directors' code.)

In an April 14 letter to Delaware officials, including the governor and the state attorney general, the association deplored the museum's proposed sale.

Such an act "will irrevocably damage its mission and ability to serve its community," wrote association president Timothy Rub, director of the Philadelphia Museum of Art.

"Furthermore, such actions can only serve to discourage those who would otherwise be inclined to support art museums and is therefore likely to have a significant negative impact on fundraising over time. Treating works of art from a museum's collection as financial assets not only weakens the institution taking such action, it will also do substantial harm to the field as a whole."

The museum's board said art sales are the sole way to keep it open. Board president Elva Ferrari-Graham said in a statement that "the trustees fully understand and respect museum best practices, [but] we couldn't bear voting to close. . . . [This] . . . will help us achieve financial stability."

It must be noted that, according to the directors association ethical code, the Academy of Fine Arts' sale of its Hopper was fine. "What PAFA did was perfectly legitimate," Gillman said.

Danielle Rice, former head of the Delaware Art Museum who runs Drexel's museum leadership program, said the line between legitimate and nonlegitimate museum art sales "is a very fine line."

"The whole notion of selling art to refine a collection gets abused a lot," she said. "Selling a $40 million Hopper - it's hard for people to understand why that's OK and something else isn't."

Part of the problem lies in the paradoxical nature of the museum/collecting institution. While conceived as stewards of art for the "public good," they buy and sell all the time, viewing their own collections as assets. Temple's Silk calls this a product of viewing collections as "dynamic and changing."

But once a museum, or any institution, views its holdings as assets that can be manipulated through the marketplace, the art is commodified, easily detached from time and place, easily shipped off, readily bought and sold.

Art historian Michael Leja of the University of Pennsylvania has pointed out that "even when a monastery falls on hard times, they don't sell the frescoes."

David Brownlee, chair of the graduate group in the history of art at Penn, suggested that nowadays the detachment of artworks from their specific cultural contexts is virtually inevitable.

"Maybe it has something to do with modernization and commodification. These things were created in a for-sale environment . . . in a capitalist society. They are not the implements our ancestors used as part of their ritual lives."

Leja said he envisions more sales coming.

"There are some great and historic works of art in some of Philadelphia's churches, libraries, and learned societies, but I think the writing is on the wall for them," he wrote in an e-mail exchange.

"The experience of walking into an old building and seeing William Rush sculptures or Charles Willson Peale paintings as part of the regular interior decor will become less and less common. That's a shame, because such experiences remind us that these buildings were frequented by these artists and that these institutions have pursued through tumultuous times the principles on which the city was founded. One of those principles was that art was integral to science, philosophy, religion, and social life."