“While lying on the beach in Nice one day, eighteen-year-old Yves Klein and his friends decided to divide the world up among themselves. Klein (1928-1962) chose the air, the cloudless sky. He remained fascinated with the element and its immaterial quality throughout his life. In the late fifties, he and the German architect Werner Ruhnau developed plans for an “architecture of air” composed of walls and roofs of air-as represented, for example, in the idea of the “Temple of the Elements” with fountains of water and fire and a café protected against the rain only by air currents. Klein associated this idea with a philosophy of optimism devoted to the creation of a paradise on earth, a Garden of Eden in which human beings would be free to pursue their own interests. The publication is the first book devoted exclusively to this aspect of Yves Klein’s art. It includes reproductions of drawings and other works as well as essays and lectures on the subject. Additional articles by other authors emphasize the significance of Klein’s work to the theme of the immaterial. Exhibition schedule: MAK Center for Art and Architecture, Schindler House, Los Angeles, May 12 – August 29, 2004.” (hatjecantz.de/yves-klein-1373-1.html)
“It’s worth pointing out, of course, that immaterial art has a long history stretching back to the 20th century. Yves Klein exhibited an empty gallery space in 1958 and envisioned an “architecture of air” a couple of years later. Tom Friedman installed an invisible object atop a plinth in 1992—and it sold for £22,325 nine years later.”
Recently (Spring 2021), Salvatore Garau showed (and sold), BUDDHA IN CONTEMPLATION: an installation: the empty space above a white square space,.  Garau wrote, “You do not see it but it exists; it is made of air and spirit. It is a work that asks you to activate the power of imagination, a power that anyone has, even those who don’t think they have it. Just as music, songs or prayers help us to see what we do not see, so even a title feeling is enough to make us view and perceive an existence. It doesn’t matter whether it is visible or not, this form generated by thought is here now, above the white square space, exactly 25 meters in front of the entrance to the Gallerie d’Italia di Piazza della Scala in Milano city, Italy, Now it exists and will remain in this space forever.”

Garaus’ claim to be original in this concept was challanged by Tom Miller … “a performance artist from Gainesville, Florida, … says that, in 2016, he installed his own invisible sculpture in Gainesville’s Bo Diddley Community Plaza, an outdoor event space. He titled it Nothing and erected it over the course of five days with a team of workers who moved blocks of air like mimes building the Great Pyramid of Giza. Tens of people were on hand to see the opus unveiled that June. 

Miller even made a short film about the work, a mockumentary that features fake artists and curators as talking heads. He compares his respective take on nothingness to John Cage’s “4′33″ and Seinfeld

 “All I can say personally is that Nothing is very important to me,” Miller told Artnet News in an email. “I should be credited with Nothing (specifically the idea of Nothing fashioned into sculpture form), and Gainesville, Florida—not Italy—is where Nothing happened first.”

Can a phenomenon be perceived as good art.  (There is a problem with post hoc rationalizing the expression of an artistic impulse).  Can art be right for the wrong reasons?   The issue of the artist’s state of mind or intentions–conscious or otherwise–rises up again:  The mainspring of creation might be a mere concept, a joke, or conscious duplicity.  We must consider again the intentionality of the artist as part of the meaning of the artwork.

Meaning derives from connections–as Garau said of his “invisible” sculpture, “You do not see it but it exists; it is made of air and spirit.” .

AIR is intimately related to breath—the breath of life: “From Middle English spirit, from Old French espirit (spirit), from Latin spīritus (breath; spirit), from Proto-Indo-European *(s)peys- (to blow, breathe). Compare inspirerespiretranspire, all ultimately from Latin spīrō (I breathe, blow, respire). Displaced native Middle English gast (spirit) (from Old English gāst (spirit, ghost)), whence modern English ghostDoublet of sprite. (https://en.wiktionary.org/wiki/spirit )