INTENTIONALITY o Intentionality is the property of being about something, having content. In the 19th Century psychologist franz Brentano re-introduced this term from Medieval philosophy and held that intentionality was the mark of the mental Beliefs and desires are intentional states: they have propositional content(one believes that p one desires that pINTENTIONALITY  Intentionality is the property of being about something, having content. In the 19th Century, psychologist Franz Brentano re-introduced this term from Medieval philosophy and held that intentionality was the “mark of the mental”. Beliefs and desires are intentional states: they have propositional content (one believes that p, one desires that p)