Frankfort school
Critical theory is a school of thought which emphasizes the contemplative evaluation and analysis of society and culture by implementing principles from the humanities and social sciences.
As a phase, critical theory has two definitions with different sources and histories: The first introduced in sociology and the second introduced in literary criticism.
Critical theory is used and implemented in the sense which can describe a philosophy founded upon critique. Thus, the scholar Max Horkheimer explained a theory as critical which attempts "to release human beings from the conditions that enslave them".