As the title suggests, the essay treats art as a vehicle for a certain kinds of “subject”—as opposed to art as a discipline or set of practises. Tupper focuses in particular on “High Art” and its relation to subjects that would be proper to it. He connects those subjects to what he calls Nature, which he opposes to models derived from previous artistic practise. By Nature he means something like what Heidegger means by Dasein. The essay develops in a slow, not to say prolix and meandering, way toward a consideration of “the highest” subjects proper to High Art. These are “every thing or incident in nature which excites, or may be made to excite, the mind and heart of man as a mentally intelligent, not as a brute animal” (18). Like other PRB members, Tupper singled out Raphael for criticism as the source of art's movement from religious to heathen subjects.

WMR observed at the time that the essay seemed to him “argued on deducation from the most abstract propositions in the manner of a philosophical dissertation” (Fredeman 29, entry for 24 November 1849). In his Introduction to the 1901 facsimile reprint of the periodical, WMR is critical of Tupper's prose work: “Mr. Tupper was, for an artist, a man of unusually scientific mind; yet he was not, I think, distinguished by that power of orderly and progressive exposition which befits an argument” (page 16). These seem fair assessments, as does his subsequent comment: “The views expressed by Mr. Tupper in these two papers should be regarded as his own, and not by any means necessarily those upheld by the Pre-Raphaelite Brotherhood” (page 17). WMR's caveat probably reflects his dissent from Tupper's sharp distinction between High and Low art, and his implicit argument that simple descriptive work deals with a relatively minor subject matter. Nevertheless, the essay clearly espouses ideas that are congruent with PRB thought in a general way.