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 (Aristotle's Poetics is an often cited early example), ancient India (Bharata Muni's Natya Shastra), ancient Rome (Longinus's On the Sublime) and medieval Iraq (Al-Jahiz's al-Bayan wa-'l-tabyin and al-Hayawan, and ibn al-Mu'tazz's Kitab al-Badi). The aesthetic theories of philosophers from ancient philosophy through the 18th and 19th centuries are important influences on current literary study. The theory and criticism of literature are tied to the history of literature.
However, the modern sense of "literary theory" only dates to approximately the 1950s when the structuralist linguistics of Ferdinand de Saussure began to strongly influence English language literary criticism. The New Critics and various European-influenced formalists (particularly the Russian Formalists) had described some of their more abstract efforts as "theoretical" as well. But it was not until the broad impact of structuralism began to be felt in the English-speaking academic world that "literary theory" was thought of as a unified domain.
In the academic world of the United Kingdom and the United States, literary theory was at its most popular from the late 1960s (when its influence was beginning to spread outward from universities such as Johns Hopkins, Yale, and Cornell) through the 1980s (by which time it was taught nearly everywhere in some form). During this span of time, literary theory was perceived as academically cutting-edge, and most university literature departments sought to teach and study theory and incorporate it into their curricula. Because of its meteoric rise in popularity and the difficult language of its key texts, theory was also often criticized as faddish or trendy obscurantism (and many academic satire novels of the period, such as those by David Lodge, feature theory prominently). Some scholars, both theoretical and anti-theoretical, refer to the 1970s and 1980s debates on the academic merits of theory as "the theory wars".
By the early 1990s, the popularity of "theory" as a subject of interest by itself was declining slightly (along with job openings for pure "theorists") even as the texts of literary theory were incorporated into the study of almost all literature.Mark Bauerlein continue to argue that less capable theorists have abandoned proven methods of epistemology, resulting in persistent lapses in learning, research, and evaluation. Some scholars do draw heavily on theory in their work, while others only mention it in passing or not at all; but it is an acknowledged, important part of the study of literature.
By 2010, the controversy over the use of theory in literary studies had quieted down, and discussions on the topic within literary and cultural studies tend now to be considerably milder and less lively. However, some scholars like