The following is the first paragraph of the chapter "The Good Samaritan" in Tim Parks's novel Goodness. It appears about two-thirds of the way through the novel. George (the narrator) and his wife Shirley have a seriously handicapped daughter, Hilary, who cannot speak and has hardly developed beyond infancy:
January 1988. Hilary is five. Feeding her this morning, I thought: 'We get less change out of her than one would out of a three-week-old puppy.' I alternate between this ruthless realism and cloying sentimentality. The girl is so constipated that sometimes we have to hook a finger into her anus and lever the turds out. Shirley does this. I simply can't.
Like many a novel's narrator, George does not always have a very accurate vision of himself, but here he is right on target: he does swing between a "ruthless realism" that asserts his clear understanding of the world's difficulties and a "cloying sentimentality" that would conceal those difficulties in favor of an easier perspective.
The "change" he would like to "get out of" Hilary refers to childhood development: a puppy would develop faster than Hilary would. Since George had not wanted to have children, the reference to a puppy also recalls couples who stereotypically get a dog when they are "not ready for children." But what he and Shirley actually have to "get out of her" is her constipated shit, and it is in terms of shit that the contrast between realism and sentimentality is most fully realized here.
In a sense, "realism" appears here in the very fact that shit is mentioned at all, and it becomes "ruthless" in the explicitness with which George describes the "levering out" of the "turds." In contrast, George's "sentimentality" is somewhat concealed, only becoming clear in the final contrast between Shirley and himself: it is not both of them ("we") who do the dirty work but just Shirley. George wants to be a "ruthless realist," but when it comes to shit, he "simply can't" handle it.
The "realist," then, is beaten by the sentimentality his demonstrative "ruthlessness" is meant to combat. In his memoir Youth, J. M. Coetzee writes that "ruthless honesty is not a hard trick to learn." (See also this post.) Here, in Parks's novel, "ruthless realism" also ends up looking like a trick, and a relatively easy one at that: if you make a nasty joke and talk about your handicapped daughter's shit, then you are being "ruthless," even if it is your wife who actually cleans up the mess.
The "realistic" and the "sentimental" are also literary categories. Chronologically, the "sentimental" novel came first, in the eighteenth century, while literary "realism" emerged in the nineteenth century. In a simplified version of literary history, "realism" trumped the "sentimental" precisely by being "ruthless" rather than "cloying," and that is precisely the tendency of the "trick" of "ruthless honesty": it aims to produce a "realism" that trumps feelings.
But the slippery nature of this "hard trick" is clear in this passage. George plays tough, but is not really tough enough to face up to the challenge posed by his handicapped daughter. From the perspective of Parks's novel, the history of the genre is not the replacement of the sentimental by the realistic; rather, fiction "alternates" between the realistic and the sentimental. "Realism" would like to be "ruthless" enough to defeat "sentimentalism," but its tricks are never-ending attempts to conceal its own sentimental side. Let's talk tough about shit, but someone else has to actually dispose of it -- and the people who have to do so are those otherwise dismissed as "sentimental."