I’ve finally tracked down the primary sources of Marcel Duchamp‘s frequently cited disparagement of what he calls “retinal” art .
And I’d almost forgotten, but the best illustration to the antiretinal position of Duchamp is the eye and razor scene (above) from Un chien andalou, which I first posted back in 2007.
Also remarkable is the fact that Duchamp was actually not original when dissing “retinal painting” in the 1950s. In the 1912 pamphlet Du “Cubisme”, two hardline cubists, Albert Gleizes and Jean Metzinger, had already accused Courbet of having “accepted everything that his retina communicated to him, without intellectual control.”
See also: ocularcentrism and “The Disenchantment of the Eye: Surrealism and the Crisis of Ocularcentrism” by Martin Jay.
It’s nice to find a Google query with more hits in Google Books than in Google itself.
Such is the case with “libri idiotarum,” 47 hits in Google  and 215 in Google Books (see also the Google NGram view.)
“Libri idiotarum” means “books of the ignorant” or “books for the illiterate” (idiot did not mean what it means today). The expression was first recorded in a letter by Pope Gregory I:
“For pictorial representation is made use of in Churches for this reason; that such as are ignorant of letters may at least read by looking at the walls what they cannot read in books.”
Gregory refers to paintings, illustrations, sculpture and other visual representations used in Christian art to spread the the gospel in an era when only the clergy and the nobility were able to read.
For these unfortunate illiterate souls, the biblia pauperum (an illustrated bible) was also made.
But apart from being literate or illiterate, a picture is worth a thousand words.
Illustration: Triumph of Christianity