In the first chapter of his 2005 book, Realist Vision, Peter Brooks writes:
With the rise of the realist novel in the nineteenth century, we are into the age of Jules Michelet and Thomas Carlyle, of Karl Marx and John Ruskin, of Charles Darwin and Hippolyte Taine: that is, an age where history takes on new importance, and learns to be more scientific, and where theories of history come to explain how we got to be how we are, and in particular how we evolved from earlier forms to the present. It is the time of industrial, social and political revolution, and one of the defining characteristics of realist writing is I think a willingness to confront these issues. England develops a recognizable "industrial novel," one that takes on the problems of social misery and class conflict, and France has its "roman social," including popular socialist varieties.
To the extent that Brooks wants to link the rise of realist fiction to the rise of science and "theories of history," I can't really see how the former is influenced much by the latter, except specifically in the fiction of naturalist writers such as Emile Zola or, in the United States, Frank Norris and Theodore Dreiser. These writers did indeed try to depict human behavior as it was defined by science--especially Darwinism--and by the forces of history. But these were writers who were deliberately using realism to illustrate a view of human life as determined by such external forces, not exploring the purely literary possibilities of realism as a still relatively new aesthetic strategy. They may have in a sense been portraying "things as they are," but they were doing it from an abstract philosophical perspective, not as an attempt to first of all render life in all of its particularities.
I equally don't understand why a defining feature of realism would be the willingness to "confront" issues or to "take on" social problems. If works of fiction are truly "realistic," immersed in the details of life as lived, they will naturally, sooner or later and in one way or another, engage with the issues and the problems of the times. There is no need to take that extra step, to insist that "issues" be confronted, unless the writer's (and the critic's) real interest lies in "taking on" social problems, on using fiction as a tool of social amelioration rather than regarding it as a self-sufficient form of literary art. To me, a "defining characteristic" of any fiction that can make a claim to be literary art, that can still be taken seriously in the long run, after the "social problems" of the day have been replaced by the next set, is that it not "confront" any issues or problems other than the literary problems immediately at hand.
Brooks's own insistence here that realism must "take on" larger social and cultural questions is actually contradicted, it seems to me, by what he asserts just a few paragraphs later:
You cannot, the realist claims, represent people without taking account of the things that people use and acquire in order to define themselves--their tools, their furniture, their accessories. These things are indeed part of the very definition of "character," of who one is and what one claims to be. The presence of things in these novels also signals their break from the neoclassical stylistic tradition, which tended to see the concrete, the particular, the utilitarian as vulgar, lower class, and to find beauty in the generalized and noble. The need to include and to represent things will consequently imply a visual inspection of the world of phenomena and a detailed report on it--a report often in the form of what we call description. The descriptive is typical--sometimes maddeningly so, of these novels. And the picture of the whole only emerges--if it does--from the accumulation of things.
This seems to me a pretty good account of what the best realist novels do: Draw the reader into a meticulously described world that the reader can accept as like the "real" world (keeping in mind that realistic description in fiction is just another device the writer can use, no more "authentic" than any other, given that what the reader is finally "confronted" with are just words on a page) and allow the reader to "see" the approximated world as fully as possible. If this sort of realism does bear philosophical implications, they are centered around the idea that the real is what is perceived. (Later, the "psychological" realists such as Woolf and Joyce would reject this; their fiction finds the real in how things are perceived, by focusing on the internal processes of consciousness.) But finally the art of realism lies in the way "things" are organized, in the manner and the skill with which the writer entices the reader to take note of the illuminating details.
Such an approach seems wholly at odds with the notion that realist fiction makes the reader aware of historical abstractions and social "issues." (The "generalized" rather than the "concrete.") "Things as they are" in the one seem on a wholly different scale than "things as they are" in the other. We can be made aware in fiction, subtly if implicitly, of historical change or social conflict, but only by acknowleding that the "defining characteristic" of realism is its particular approach to aesthetic representation, not its willingness to "take on" non-literary "problems." I am still reading Brooks's book, and I hope he will demonstrate to me how these two discrepant impulses can be reconciled in an account of literary realism.