Next fall, some of the most provocative artists in the world will come to Philadelphia to create public sculptures and installations.

People like Ai Weiwei of Beijing, Tania Bruguera of Cuba, Tyree Guyton of Detroit, and Zoe Strauss of Philadelphia have provoked their governments or transformed their urban landscape. Now they have been invited to re-invent what a public monument should be.

A public art project called the Monument Lab, in partnership with Mural Arts Philadelphia, announced a roster of 22 artists to create work that will be installed in public squares and parks.

"We're pinching ourselves over this roster," said artistic director Paul Farber. He asked all of them to respond to the same question:

What is an appropriate monument for the current city of Philadelphia?

"Monuments traditionally appeal to the idea of the eternal. They are statements of power, of legacy, that are permanent and universal," said artistic director Paul Farber. "For us, we're starting from the point of view that our civic institutions are important to us, but they are changing. Monuments need to change, too."

Most of the installations will be temporary, flexible, and have some kind of civic engagement element. Some of the artists are well-known for their positions on social justice and human rights. Their artwork has gotten them arrested by their governments.

The work of the two-dozen artists will fall loosely into five themes: immigrations, education, restorative justice, opioid addiction, and public space.

"They are addressing issues of social justice, including issues of race, gender, sexuality, class, and national belonging," said Farber. "Some of them are exploring those ideas in traditional sculptural form. Others are seeking the ephemeral - whether light, sound, projection or dialogue itself."

What, exactly, the artists are going to produce is still to be determined. They project will be unveiled in public parks around the city in September.

The artists who have accepted the invitation are:

Tania Bruguera, Havana/New York City/Cambridge
Mel Chin, Egypt, North Carolina
Kara Crombie, Philadelphia
Tyree Guyton, Detroit
Hans Haacke, New York City
David Hartt, Philadelphia
Sharon Hayes, Philadelphia
King Britt and Joshua Mays, Philadelphia and Oakland
Klip Collective, Philadelphia
Duane Linklater, North Bay, Ontario
Emeka Ogboh, Lagos/Berlin
Karyn Olivier, Philadelphia
Michelle Angela Ortiz, Philadelphia
Kaitlin Pomerantz, Philadelphia
RAIR featuring Abigail DeVille, Philadelphia and New York City
Alexander Rosenberg, Philadelphia
Jamel Shabazz, New York City
Zoe Strauss, Philadelphia
Hank Willis Thomas, New York City
Shira Walinsky and Southeast by Southeast, Philadelphia
Ai Weiwei, Berlin/Beijing
Marisa Williamson, New York City