This is the term used by Aristotle in his Poetics to explain the existence (and function) of ancient Greek tragedy. Aristotle saw tragic drama not as an instrument for the articulation and clarification of a specific site of conflict (and therefore not as a dialectical activity) – but rather as a way of purging or purifying the emotions of an audience.

In late 19^th century psychology, of course, this Greek term was taken by Sigmund Freud – and is now generally applied to the curative release of suppressed emotions that have caused some kind of emotional tension or anxiety. The early work of Freud and Breuer (with particular reference to the clinical state of hysteria) used hypnosis as a means of treatment.

Under hypnosis, certain patients were able to relate and re-experience conflicts and emotion-producing incidents that their conscious minds had repressed. Bringing such sub-conscious events and experiences to the ‘surface’ of the mind enabled certain patients to release tensions – and so reduced the apparent symptoms of their psychosis.

Taking his term directly from Aristotle, Freud called the technique "cathartic therapy". In later case-studies, he achieved the effect of ‘catharsis’ without recourse to hypnosis, and followed a line of interrogation (called ‘free association’) with his patients instead.

In both Aristotelian poetics and Freudian psychology, then, the process of ‘catharsis’ is one in which repressed emotions are consistently brought to a conscious level (either by ‘free association’ (as in Freud), or by witnessing evocative stage spectacle (as in Aristotle’s understanding of the function of tragedy)). The contention behind both theories is that the rational, discursive and dialectical approach to confronting deeply repressed feelings (or events) can sometimes appear to bring relief, but that only catharsis (as a result of psychological therapy or the spectorship of liminal theatrical activity) can lead to a long-lasting elimination of mental or moral problems.