Intentionality, originally a concept from scholastic philosophy, was reintroduced in contemporary philosophy by the philosopher and psychologist Franz Brentano in his work Psychologie vom Empirischen Standpunkte. While often simplistically summarised as "aboutness", Brentano defined it as the main characteristic of psychical phenomena, by which they could be distinguished from physical phenomena. Every mental phenomenon, every psychological act is directed at a content, has an object. Every belief, desire etc. has an object that they are about: the believed, the wanted. This object is commonly referred to as the intentional object.
Through the works of Husserl, who took it over from Brentano, the concept of intentionality received more widespread attention in current philosophy, both continental and analytic.
In current Artificial Intelligence and Philosophy of mind it is a controversial subject and thought to be something that a machine will perhaps never achieve.
N.B. intentionality (-tion-) is not to be confused with intensionality (-sion-), a concept from semantics.
See also: Chinese Room, Thomas Nagel, consciousness, mind-body problem, John Searle
