Harding was also a prodigious writer of books on art. Two years after the publication of Modern Painters I, he brought out his Principles and Practice of Art (1845). In the book he included a generous comment to Ruskin in a footnote:
My observations on the defects of the old landscape painters, will be chiefly confined to composition and light and shade; even these I shall limit very much, as the Graduate of Oxford, in his work entitled" Modern Painters..." has already anticipated me in a most able manner. (see Harding, The Principles and Practice of Art, p.65).
Tim Hilton points to differences between the two men which later emerged:
See for instance, the similarities between MP1 and Harding's The Principles and Practice of Art, 1845. There are a number of stories of Harding's later opposition to Modern Painters. Ruskin claimed that Harding was jealous of the position given to Turner... Henry Holiday describes a Harding drawing class in 1858. Holiday had been drawing a large landscape from nature.' "What", [Harding] said," are you a Pre-Raphaelite?" "I am." The diplomatic sky darkened and his face was itself a declaration of war. He at once attacked what he assumed to be my main body, viz., Mr Ruskin, and opened fire with two charges. Ist, that the writings of his renegade pupil were a mass of pernicious heresies; and 2nd, that they were merely a re-cook of his (Mr Harding's) own works on art...' Henry Holiday, Reminiscences of my Life, 1914,49. ( Hilton, John Ruskin The Early Years p. 283).