First, these terms deal with the sociological aspects of literature—in what societies and social conditions the characters live and the actions take place. The author of a piece of literature may have several motives for creating a piece, and one of them is very often an exposure or examination of his/her society, or a society symbolically like the author’s own. This is not always the case, of course, but in novels such as Dickens’ or Balzac’s for example, or in the plays of Ibsen and Chekhov, the social commentary on the status of the characters is part and parcel of the reason for the creation of the literature. Novelists and poets are not primarily reformers of their societies, but very often give a voice to those who are seeking change—see Hugo’s Les Miserables or Orwell’s (non-fiction) work, Down and Out in London and Paris for examples. In poetry these social questions are most often ignored (of course here too there are many exceptions) because by definition Poetry is more a first-person expression of singular experiences.
Secondly, the terms signify hidden agendas for the authors, often hidden even to them. Take, for example, the anti-feminist rhetoric of nineteenth-century fiction only exposed when scholars learned to deconstruct the text and discern the assumptions made about gender, about status of the agent of rhetoric, etc., that lay in the choices of vocabulary and syntax. Race, assumedly an open and conscious choice by an author, actually has all kinds of assumptions built into those choices—look at Tom Sawyer and the assumptions made because the boy is accompanied by a black man; or look at To Kill a Mockingbird and the reader’s fear of Boo. As for class, every novel is, in a sense, an “Upstairs, Downstairs” novel, in which the life-styles of the classes form a canvas on which are painted their differences and similarities.
Third, the gender, race, and class of the reader make each reader unique, even though they are all reading the same text. How does an Indian read Passage to India differently from a white European? What is a native American’s reaction to the poem Hiawatha? How would a chauffeur see The Great Gatsby? Etc. So all these terms must be considered in scholarship and reviews, and especially in pedagogy. Can Little Black Sambo be taught next to Grimm’s Fairy Tales, or Rapunzel be taught next to Jack and the Beanstalk without any mention of the students’ race, gender, etc.?