Please give clear definitions of Marxism, Modernism, New Criticism and Postcolonialism.
Marxist criticism considers literature as inseparable from history and from the social practices of the era in which literary works are produced and/or interpreted. Because history is the field of struggle between those who own the means of production (the bourgeosie) and those who work for this class (the working class), literature bears the mark of such struggle.
Modernism is the collective name usually given to the avant-garde movements that developed at the beginning of the twentieth century and revolutionized cultural production. Because of the diversity of these movements (Symbolism, Post-Impressionism, Expressionism, Futurism, Imagism, Vorticism, Dada and Surrealism), it is sometimes argued that we should speak of Modernisms in the plural. However, all these movements share a concern with experimentation and with artists' freedom from realist constraints. The move away from realism takes Modernist investigation towards the human psyche. Modernist production tends to reflect this investigation with literary techniques such as the stream of consciousness, the interior monologue and the non-linear, non-chronological and fragmented character of its narratives.
New Criticism is a (mainly) American school of criticism that developed after the Second World War and was founded by critics such as John Crowe Ransom, Cleanth Brooks, R. P. Blackmur, Allen Tate and Robert Penn Warren. It privileged poetry above other literary genres and, building on T.S. Eliot's words, it aimed to understand "poetry as poetry and not another thing"). New Criticism thus reacted against historicism and the efforts to make the historical context relevant to the reading of a work of art. According to the new critics, a work of art must be read as a closed system whose significance resides within itself. New Critics valued in particular poems that made use of ambiguity, paradox and irony.
Initially inspired by the work of Edward Said, Postcolonialism critiqued the cultural assumptions of imperialism and the West's supposedly civilizing mission towards the East. It exposed the systematic stereotyping of the East. More recent developments, however, also celebrated the cultural difference of former colonial subjects, thus decentering the literary canon in favor of the contributions coming from the margins of the empire.