It's hard to imagine a time when Realism (with a capital R) was a revolutionary art movement. We tend to think of it as perhaps the most conservative type of art there is. Yet, in France, in the 1830s through the 1860s, it was very much a liberal cause, espoused by artist such as Gustave Courbet, Jean-Francois Millet, and Honore Daumier. Very well, if Realism was revolutionary, what then, pray tell, was the nature of that art to which it was reactionary? To understand the art of mid-nineteenth century France, perhaps a cartoon-like drawing done by Honore Daumier might serve to enlighten us. It depicts two well-dressed, but quite homely Paris matrons amongst a crowd at the 1864 Salon as they turn their eyes from the dozens of luscious female nude paintings hung frame to frame on the wall behind them. The quotation reads, "This year, Venuses again...Always Venuses!", the implication being that idealized Venuses were NOT reality or Realism.
How then did the French Realists DEFINE Realism? Well, certainly it was a painting style, a naturalism, unadorned by decoration or obvious idealization. But then realism or naturalism of this kind had, to one degree or another, been around for centuries. What made French Realism revolutionary was it's sojourn into contemporary subject matter and specifically it's political bent toward socialism and the plight of the laboring masses. Realism was thus a handmaiden for the socialist political activists of the time attempting to shake up the bourgeoisie (middle classes) in order to spearhead social changes leading to an idealistic "golden age of humanity". It was a not-so-subtle use of art for propaganda purposes.
Courbet's The Stone Breakers of 1849, Millet's The Gleaners of 1857, and Daumier's The Third-Class Carriage of 1862 are all examples of this type of Realism. However such was the nature of the political ebb and flow during this period in France that the Socialist political movement came and went leaving the Realist ART movement as something of a bathtub ring denoting it's high-water mark. The irony is that Realism turned out to have more substance than did it's political proponents. It marked the first significant revolt on the part of painters against the conservative, academic, classical, history-painting, Venus-painting art establishment, almost a full generation before Manet, Monet, Cezanne, Pissarro, and others mounted their attacks. In effect, the Realist artists spearheaded not political changes, but artistic changes, and served as models and heros for the beleagered Impressionist marching in their wake.