William Blake took particular offense with Reynolds' Discourses on Art. The two had radically different views on the role of art, Blake believing that men were born with artistic knowledge while Reynolds arguing that such knowledge was only gained from experience.

Collins alludes to Blake's famously harsh annotations of Reynolds (see this article from the Andrew Graham-Dixon archive for more). On the title page of Discourses on Art, Blake wrote, “This Man was Hired to Depress Art.” Later he went further:
Having spent the vigour my Youth & Genius under the Oppression of Sr Joshua & his Gang of Cunning Hired Knaves Without Employment & as much as could possibly be Without Bread, The Reader must Expect to Read in all my Remarks on these Books Nothing but Indignation & Resentment. While Sr Joshua was rolling in Riches, Barry was Poor & Unemploy’d except by his own Energy; Mortimer was call’d a Madman, & only Portrait Painting applauded by the Rich & Great ... Fuseli, Indignant, almost hid himself. I am hid.