Brentano has introduced into modern psychology a well known concept from medieval philosophy, but has almost forgotten, further on, the concept of the intentional act or, in brief, the "act."
Brentano and his followers tell us that every psychical or conscious "thing" consists of four parts : the I, the act, the content and the object. They further tell us that the act may have different forms, such as thinking, assuming willing, etc.
(Hans Driesch, The Crisis in Psychology, London, Princeton, 1925, p. 164)
* * *
.. Husserl does not assume, as does Brentano, that all psychical phenomena are "act" phenomena, but he admits psychical phenomena without "intention<' as e.g., sensation, i.e.., he admits that these phenomena are merely erlebt. I reply that these phenomena are also, no doubt, consciously had, and that to this extent they are act-phenomena, because having consciously is the act. [etc]
(ibidem, p. 165)
