"Marxism is a sociological approach to literature that views works of literature as the products of historical forces that can be analysed by looking at the material conditions in which they were formed.” Evaluate the importance of Marxist Criticism to the study of literature as a whole.
One way to go about answering the question of the importance of Marxist criticism to the study of literature is to look at the many iterations and extensions of Marxist criticism, some of which have come to dominate academic discourse (regarding literature at least) for the past several decades.
Feminist literary criticism, as a loose body of various schools of thought, is seen as an outgrowth of Marxist criticism. Deconstruction also has some roots in Marxist thought, as do the highly influential theories of Michel Foucault. A central focus of each of these modes of criticism and academic discourse relates to the notion of power.
While it is true that Marxist philosophy was initially interested in economics (and the political relationships inherent in economic systems), Marxist theories in the 20th century were closely associated with the notions of discourse and ideology. Language became both a "material" to be studied, questioned, and parsed, and a sign or product of power relationships and class conflicts. To put it another way, language for Marxist critics is an ideological tool or even an ideological machine.
[A]lthough he did not expound in detail on the connections between literature and society, it is agreed among most scholars that Marx did view the relationship between literary activity and the economic center of society as an interactive process. (eNotes)
Feminist critical theory, deconstruction and Foucault in particular each looked at ways in which language and narrative were indications of power relationships, social economies if you will, wherein a "dominant ideology" was nearly always on display, forwarding itself through implication, insinuation, and presumptions of normalcy. The term "dominant ideology" is important to Marxist criticism and, according to scholar Raymond Williams, can be defined as a "'whole social process" and one in which a "system of meanings and values is the expression or projection of a particular class interest" (Marxism and Literature).
Marxist criticism proposes that the "social process" of ideology is on display in literature. The role of women in narratives is discussed widely in feminist criticism as are the implied and often vaunted "male" values of rationality and aggressive behavior (as in Helene Cixous' famous essay, "The Laugh of the Medusa"). Toni Morrison has written about the terminology of race that exists in common modes of the English language which activates and perpetuates racial bias, pointing to certain color-based terms and their connotations, both positive and negative, and suggesting that ethnic prejudice and the politics of race are to some extent built into the language.
If Marxist criticism pointed the way to analyzing literature in terms of its demonstration of social processes, social economies and power dynamics, we can argue that Marxist criticism opened the door to feminist criticism, queer theory, post-colonial criticism, and other modes of reading and assessing literature. In this way, Marxist criticism has contributed immensely to 20th century academic discourse(s) surrounding literature and film and other cultural products, informing these discourses with basic questions regarding the relationships between language and power and social structures.