case for perception, for example, which involves sensory impressions that represent what the world is like. this representational aspect is usually understood as involving a propositional attitude. closely related to these distinctions is the concept of intentionality. intentionality is usually defined as the characteristic of mental states to refer to or be about objects or states of affairs. the belief that the moon has a circumference of 10921 km, for example, is a mental state that is intentional in virtue of being about the moon and its circumference. it is sometimes held that all mental states are intentional, i.e. that intentionality is the "mark of the mental". this thesis is known as intentionalism. but this view has various opponents, who distinguish between intentional and non-intentional states. putative examples of non-intentional states include various bodily experiences like pains and itches. because of this association, it is sometimes held that all sensory states lack intentionality. but such a view ignores that certain sensory states, like perceptions, can be intentional at the same time. it is usually accepted that all propositional attitudes are intentional. but while the paradigmatic cases of intentionality are all propositional as well, there may be some intentional attitudes that are non-propositional. this could be the case when an intentional attitude is directed only at an object. in this view, elsie's fear of snakes is a non-propositional intentional attitude while joseph's fear that he will be bitten by snakes is a propositional intentional attitude. conscious and unconscious a mental state is conscious if it belongs to phenomenal experience. the subject is aware of the conscious mental states it is in: there is some subjective feeling to having them. unconscious mental states are also part of the mind but they lack this phenomenal dimension. so it is possible for a subject to be in an unconscious mental state, like a repressed desire, without knowing about it. it is usually held that some types of mental states, like sensations or pains, can only occur as conscious mental states. but there are also other types, like beliefs and desires, that can be both conscious and unconscious. for example, many people share the belief that the moon is closer to the earth than to the sun. when considered, this belief becomes conscious, but it is unconscious most of the time otherwise. the relation between conscious and unconscious states is a controversial topic. it is often held that conscious states are in some sense more basic with unconscious mental states depending on them. one such approach states that unconscious states have to be accessible to consciousness, that they are dispositions of the subject to enter their corresponding conscious counterparts. on this position there can be no "deep unconscious", i.e. unconscious mental states that can not become conscious. the term "consciousness" is sometimes used not in the sense of phenomenal consciousness, as above, but in the sense of access consciousness. a mental state is conscious in this sense if the information it carries is available for reasoning and guiding behavior, even if it is not associated with any subjective feel characterizing the concurrent phenomenal experience. being an access-conscious state is similar but not identical to being an occurrent mental state, the topic of the next section. occurrent and standing a mental state is occurrent if it is active or causally efficacious within the owner's mind. non-occurrent states are called standing or dispositional states. they exist somewhere in the back of one's mind but currently play no active role in any mental processes. this distinction is sometimes identified with the distinction between phenomenally conscious and unconscious mental states. it seems to be the case that the two distinctions overlap but do not fully match despite the fact that all conscious states are occurrent. this is the case because unconscious states may become causally active while remaining unconscious. a repressed desire may affect the agent's behavior while remaining unconscious, which would be an example of an unconscious occurring mental state. the distinction between occurrent and standing is especially relevant for beliefs and desires. at any moment, there seems to be a great number of things we believe or things we want that are not relevant to our current situation. these states remain inactive in the back of one's head even though one has them. for example, while ann is engaged in her favorite computer game, she still believes that dogs have four legs and desires to get a pet dog on her next birthday. but these two states play no active role in her current state of mind. another example comes from dreamless sleep when most or all of our mental states are standing states. rational, irrational and arational certain mental states, like beliefs and intentions, are rationally evaluable: they are either rational or irrational depending on whether they obey the norms of rationality. but other states, like urges, experiences of dizziness or hunger, are arational: they are outside the domain of rationality and can be neither rational nor irrational. an important distinction within rationality concerns the difference between theoretical and practical rationality. theoretical rationality covers beliefs and their degrees while practical rationality focuses on desires, intentions and actions. some theorists aim to provide a comprehensive account of all forms of rationality but it is more common to find separate treatments of specific forms of rationality that leave the relation to other forms of rationality open. there are various competing definitions of what constitutes rationality but no universally accepted answer. some accounts focus on the relation between mental states for determining whether a given state is rational. in one view, a state is rational if it is well-grounded in another state that acts as its source of justification. for example, scarlet's belief that it is raining in manchester is rational because it is grounded in her perceptual experience of the rain while the same belief would be irrational for frank since he lacks such a perceptual ground. a different version of such an approach holds that rationality is given in virtue of the coherence among the different mental states of a subject. this involves an holistic outlook that is less concerned with the rationality of individual mental states and more with the rationality of the person as a whole. other accounts focus not on the relation between two or several mental states but on responding correctly to external reasons. reasons are usually understood as facts that count in favor or against something. on this account, scarlet's aforementioned belief is rational because it responds correctly to the external fact that it's raining, which constitutes a reason for holding this belief. classification according to brentano an influential classification of mental states is due to franz brentano. he argues that there are three basic kinds: presentations, judgments, and phenomena of love and hate. all mental states either belong to one of these kinds or are constituted by combinations of them. these different types differ not in content or what is presented but in mode or how it is presented. the most basic kind is presentation, which is involved in every mental state. pure presentations, as in imagination, just show their object without any additional information about the veridical or evaluative aspects of their object. a judgment, on the other hand, is an attitude directed at a presentation that asserts that its presentation is either true or false, as is the case in regular perception. phenomena of love and hate involve an evaluative attitude towards their presentation: they show how things ought to be, and the presented object is seen as either good or bad. this happens, for example, in desires. more complex types can be built up through combinations of these basic types. to be disappointed about an event, for example, can be construed as a judgment that this event happened together with a negative evaluation of it. brentano's distinction between judgments, phenomena of love and hate, and presentations is closely related to the more recent idea of direction of fit between mental state and world, i.e. mind-to-world direction of fit for judgments, the world-to-mind direction of fit for phenomena of love and hate and null direction of fit for mere presentations. brentano's tripartite system of classification has been modified in various ways by brentano's students. alexius meinong, for example, divides the category of phenomena of love and hate into two distinct categories: feelings and desires. uriah kriegel is a contemporary defender of brentano's approach to the classification of mental phenomena. academia discussions about mental states can be found in many areas of study. in cognitive psychology and the philosophy of mind, a mental state is a kind of hypothetical state that corresponds to thinking and feeling, and consists of a conglomeration of mental representations and propositional attitudes. several theories in philosophy and psychology try to determine the relationship between the agent's mental state and a proposition. instead of looking into what a mental state is, in itself, clinical psychology and psychiatry determine a person's mental health through a mental status examination. epistemology mental states also include attitudes towards propositions, of which there are at least two—factive and non-factive, both of which entail the mental state of acquaintance. to be acquainted with a proposition is to understand its meaning and be able to entertain it. the proposition can be true or false, and acquaintance requires no specific attitude towards that truth or falsity. factive attitudes include those mental states that are attached to the truth of the proposition—i.e. the proposition entails truth. some factive mental states include "perceiving that", "remembering that", "regretting that", and (more controversially) "knowing that". non-factive attitudes do not entail the truth of the propositions to which they are attached. that is, one can be in one of these mental states and the proposition can be false. an example of a non-factive attitude is believing—people can believe a false proposition and people can believe a true proposition. since there is the possibility of both, such mental states do not entail truth, and therefore, are not active. however, belief does entail an attitude of assent toward the presumed truth of the proposition (whether or not it's so), making it and other non-factive attitudes different from a mere acquaintance.