This is a conceptual art project by Praxis, curated by Vallejo Gantner, artistic director of PS122 in Manhattan.
Praxis is the collaborative art team of Brainard and Delia Carey, and in this project, James Franco has collaborated with them.
Praxis has been in the Whitney Museum Biennial and James Franco has exhibited his art work internationally. 

The Non-Visible Museum is an extravaganza of imagination, a museum that reminds us that we live in two worlds: the physical world of sight and the non-visible world of thought. Composed entirely of ideas, the Non-Visible Museum redefines the concept of what is real. Although the artworks themselves are not visible, the descriptions open our eyes to a parallel world built of images and words. This world is not visible, but it is real, perhaps more real, in many ways, than the world of matter, and it is also for sale.
http://www.nonvisiblemuseum.com
Important Note: When you contribute to this Kickstarter project, you are not buying a visible piece of art! You will not receive a painting or a film or a photograph in your mailbox. What you will receive is something even more fascinating: The opportunity to collaborate in an act of artistic creation. You will receive a title card with a description of a piece of art, as well as a letter of authentication. You may mount this card on a blank wall in your home or gallery. What comes next is up to you! The artwork comes to life—and takes on full personal meaning—in your imagining and describing of it, both to yourself and to your visitors. You may also choose to sell the non-visible artwork to another collector, to exhibit it elsewhere, or to lend it back to Praxis when we take the Non-Visible Museum on tour.

Here the informations:

As these non-visible works of art are bought, exchanged, and resold, they open our eyes to the unseen universe that exists at every moment, and we can share that universe. It is like finding the code beneath. We exchange ideas and dreams as currency in the New Economy.

In the near future we will invite more artists, writers, and others to contribute works to the Non-Visible Museum so that it can keep expanding. You can sign up on our website to be on the mailing list. http://www.nonvisiblemuseum.com

For now, we want to tour this museum in the U.S. and Europe. For each exhibition, we will give a tour of the Non-Visible Museum, describing to all those in attendance what they are looking at and imagining. As this tour grows, we will continue to collaborate and add new works. 

A MANIFESTO: TO CLARIFY THE NON-VISIBLE

1. 
Art itself is nothing.
All that matters is what is left.
The afterglow.
The ambition is to produce this.
We strive for an afterglow with no thing preceding.
A glow.
Phosphenes.

2. 
The only surface worth painting is the mind of the viewer.
The viewing of art should not require eyes.
Art should be entoptic.
We strive to force meditation.
The prisoner’s cinema.
Phosphenes.

3.
Art is without value until it faces the market.
The market purveys value.
Money is banal until it has been spent.
Money spent on art is money transformed.
Money spent is mourned.
This mourning is eased by art.
We strive to enhance mourning.
Mourning is a response to what is not there.
An afterglow.

4.
What you see does not matter.
What you have seen is everything.
All you truly buy is the afterglow.
It has value.

5.
You must pay more for the glow that has no thing.
Nothing before.
Pure after.
Phosphenes.

RULES FOR THE CREATION OF THE NON-VISIBLE
You shall not add to the banal.  (You shall not build.)
You shall not litter the world with art. (You shall not make.)
What you have not made must be beautiful.
What you have not made must have value.
You must bring what you have not made to market.
(The market will give it value.)
You must give to the market absence.
(Money is banal until spent.)
You must offer the market anguish.
(What is spent is painful.)
You must make the market beautiful.
(Nothing beautiful without pain.)
You must increase the world behind the eyes.
The wreck of the Medusa.
It left us with phosphenes.
You must conjure them and sell them.
Only when you have done this are you one of us.

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By Douglas Anthony Cooper
In accordance with Praxis
(Brainard and Delia Carey)

 by Ilaria Rebecchi