Personality disorder is a term with a distinctly modern meaning, owing in part to its clinical usage and the institutional character of modern psychiatry. The currently accepted meaning must be understood in the context of historical changing classification systems such as DSM-IV and its predecessors. Although highly anachronistic, and ignoring radical differences in the character of subjectivity and social relations, some have suggested similarities to other concepts going back to at least the ancient Greeks. For example, the Greek philosopher Theophrastus described 29 'character' types that he saw as deviations from the norm, and similar views have been found in Asian, Arabic and Celtic cultures. A long-standing influence in the Western world was Galen's concept of personality types, which he linked to the four humours proposed by Hippocrates.
