[2] The idea fell out of discussion with the end of the medieval scholastic period, but in recent times was resurrected by empirical psychologist Franz Brentano and later adopted by contemporary phenomenological philosopher Edmund Husserl.
The concept of intentionality was reintroduced in 19th-century contemporary philosophy by Franz Brentano (a German philosopher and psychologist who is generally regarded as the founder of act psychology, also called intentionalism)[4] in his work Psychology from an Empirical Standpoint (1874).
According to some interpreters the "in-" of "in-existence" is to be read as locative, i.e. as indicating that "an intended object ... exists in or has in-existence, existing not externally but in the psychological state" (Jacquette 2004, p. 102), while others are more cautious, stating: "It is not clear whether in 1874 this ... was intended to carry any ontological commitment" (Chrudzimski and Smith 2004, p. 205).
A major problem within discourse on intentionality is that participants often fail to make explicit whether or not they use the term to imply concepts such as agency or desire, i.e. whether it involves teleology.
For philosophers of language, what is meant by intentionality is largely an issue of how symbols can have meaning.
[5] In contrast to Brentano's view, French philosopher Jean-Paul Sartre (Being and Nothingness) identified intentionality with consciousness, stating that the two were indistinguishable.
[6] German philosopher Martin Heidegger (Being and Time), defined intentionality as "care" (Sorge), a sentient condition where an individual's existence, facticity, and being in the world identifies their ontological significance, in contrast to that which is merely ontic ("thinghood").
[7] Other 20th-century philosophers such as Gilbert Ryle and A. J. Ayer were critical of Husserl's concept of intentionality and his many layers of consciousness.
[13] Chisholm's writings have attempted to summarize the suitable and unsuitable criteria of the concept since the Scholastics, arriving at a criterion of intentionality identified by the two aspects of Brentano's thesis and defined by the logical properties that distinguish language describing psychological phenomena from language describing non-psychological phenomena.
[14] Chisholm's criteria for the intentional use of sentences are: existence independence, truth-value indifference, and referential opacity.
[15] In current artificial intelligence and philosophy of mind, intentionality is sometimes linked with questions of semantic inference, with both skeptical and supportive adherents.
[16] John Searle argued for this position with the Chinese room thought experiment, according to which no syntactic operations that occurred in a computer would provide it with semantic content.
This involves a commitment to modal realism, for example in the form of the Lewisian model or as envisioned by Takashi Yagisawa.
Adverbialism has been challenged on the grounds that it puts a strain on natural language and the metaphysical insights encoded in it.
Anscombe (1957), Peter Geach (1957), and Charles Taylor (1964) all adhere to the former position, namely that intentional idiom is problematic and cannot be integrated with the natural sciences.
Members of this category also maintain realism in regard to intentional objects, which may imply some kind of dualism (though this is debatable).
The latter position, which maintains the unity of intentionality with the natural sciences, is further divided into three standpoints: Proponents of the eliminative materialism, understand intentional idiom, such as "belief", "desire", and the like, to be replaceable either with behavioristic language (e.g. Quine) or with the language of neuroscience (e.g. Churchland).
Holders of realism argue that there is a deeper fact of the matter to both translation and belief attribution.
In other words, manuals for translating one language into another cannot be set up in different yet behaviorally identical ways and ontologically there are intentional objects.
Famously, Fodor has attempted to ground such realist claims about intentionality in a language of thought.
One such implication would be that there is, in principle, no deeper fact of the matter that could settle two interpretative strategies on what belief to attribute to a physical system.
In other words, the behavior (including speech dispositions) of any physical system, in theory, could be interpreted by two different predictive strategies and both would be equally warranted in their belief attribution.
This category can be seen to be a medial position between the realists and the eliminativists since it attempts to blend attributes of both into a theory of intentionality.
Dennett, for example, argues in True Believers (1981) that intentional idiom (or "folk psychology") is a predictive strategy and if such a strategy successfully and voluminously predicts the actions of a physical system, then that physical system can be said to have those beliefs attributed to it.
However, exponents of this view are still further divided into those who make an Assumption of Rationality and those who adhere to the Principle of Charity.
The latter is advocated by Grandy (1973) and Stich (1980, 1981, 1983, 1984), who maintain that attributions of intentional idioms to any physical system (e.g. humans, artifacts, non-human animals, etc.)
These two features seem to be closely related to each other, which is why intentionalists have proposed various theories in order to capture the exact form of this relatedness.
[40] A further form argues that some unusual states of consciousness are non-intentional, although an individual might live a lifetime without experiencing them.
[43] Several authors have attempted to construct philosophical models describing how intentionality relates to the human capacity to be self-conscious.