By "the sketch of manners," Baudelaire means the depiction of outward bearing or how people conduct themselves toward one another. He argues that this can best be done in art by depicting bourgeois life and the pageant of fashion.

French society was changing rapidly during Baudelaire's time of the latter nineteenth century, with the middle classes becoming wealthier and more socially prominent. According to Baudelaire, the modern artist should be in the business of capturing these changes in his artworks. But this does require considerable technical skill and expertise.

Artists have to work quickly to capture what Baudelaire calls the "daily metamorphosis of external things": in other words, the rapid transformation of aesthetic objects—people, places, things—the very stuff of which modern art is made.

Although the modern artist is primarily concerned with the fast-moving, the ephemeral, the here today and gone tomorrow, this doesn't mean that he is incapable of producing enduring works of art. On the contrary, in his sketching of contemporary manners, the talented modern artist—whose exemplar for Baudelaire is Constantin Guys—still has the remarkable ability to distill something of lasting importance from the ostensibly shallow world of contemporary French society.

As with all great artists, Baudelaire believes, Guys takes the raw material of everyday life and transforms into something enduring and eternal. In depicting contemporary life, he doesn't simply remain there; he can, through his talent and vision, transcend it.