Specific theories are distinguished not only by their methods and conclusions, but even by how they define "text." For many, "texts" means "literary (i.e. 'high' art) texts" (see literature). But different principles and methods of literary theory have been applied to non-fiction, pop fiction, film, historical documents, law, advertising, etc. In fact, some theories (e.g. structuralism) treat cultural events like fashion, football, riots, etc. as "texts."
There are many popular schools of literary theory, which take different approaches to understanding texts (which can also mean non-fiction, film, and practically anything else that can be 'read' or interpreted). Most actual theorists combine methods of more than one approach. Schools that have been historically important include new criticism, formalism and structuralism, post-structuralism, marxism, feminism, new historicism, deconstruction, reader-response criticism, and psychoanalytic criticism.
Famous practitioners from the various schools
; Hermeneutics : Friedrich Schleiermacher, Wilhelm Dilthey, Hans-Georg Gadamer,
; Marxism : Georg Lukacs, Theodor Adorno, Walter Benjamin, Raymond Williams, Terry Eagleton, Fredric Jameson
; Psychoanalytic criticism : Sigmund Freud, Jacques Lacan
; Russian Formalism : Victor Shklovsky, Vladimir Propp
; New Criticism : John Crowe Ransom, Cleanth Brooks, Robert Penn Warren
; Structuralism : Roman Jakobson, Claude Lévi-Strauss, the early Roland Barthes, Jurij Lotman
; Post-structuralism : Michel Foucault, Julia Kristeva, the late Roland Barthes, Gilles Deleuze and Félix Guattari
; Deconstruction : Jacques Derrida, Paul de Man
; Reader-response criticism : Wolfgang Iser, Hans-Robert Jauss
; Feminism : Luce Irigaray, Hélène Cixous, Elaine Showalter
; Queer theory : Judith Butler, Eve Sedgewick
; New historicism : Stephen Greenblatt
; Cultural studies : Stuart Hall
; Other : Maurice Blanchot, Harold Bloom, Erich Auerbach, Robert Graves, Alamgir Hashmi, Stanley Fish, Edward Said
History
The practice of literary theory became a profession in the 20th century, but it has historical roots that run as far back as ancient Greece (Longinus' On the Sublime is an often cited early example as is Aristotle's Poetics). Philosophers throughout the ages have commented on the nature of literature and of interpretation. So, in many ways, literary theory can be seen as a sub-school of philosophy as well as of literary history.