mental state mental state a mental state, or a mental property, is a state of mind of a person. mental states comprise a diverse class, including perception, pain experience, belief, desire, intention, emotion, and memory. there is controversy concerning the exact definition of the term. according to epistemic approaches, the essential mark of mental states is that their subject has privileged epistemic access while others can only infer their existence from outward signs. consciousness-based approaches hold that all mental states are either conscious themselves or stand in the right relation to conscious states. intentionality-based approaches, on the other hand, see the power of minds to refer to objects and represent the world as the mark of the mental. according to functionalist approaches, mental states are defined in terms of their role in the causal network independent of their intrinsic properties. some philosophers deny all the aforementioned approaches by holding that the term "mental" refers to a cluster of loosely related ideas without an underlying unifying feature shared by all. various overlapping classifications of mental states have been proposed. important distinctions group mental phenomena together according to whether they are sensory, propositional, intentional, conscious or occurrent. sensory states involve sense impressions like visual perceptions or bodily pains. propositional attitudes, like beliefs and desires, are relations a subject has to a proposition. the characteristic of intentional states is that they refer to or are about objects or states of affairs. conscious states are part of the phenomenal experience while occurrent states are causally efficacious within the owner's mind, with or without consciousness. an influential classification of mental states is due to franz brentano, who argues that there are only three basic kinds: presentations, judgments, and phenomena of love and hate. mental states are usually contrasted with physical or material aspects. for (non-eliminative) physicalists, they are a kind of high-level property that can be understood in terms of fine-grained neural activity. property dualists, on the other hand, claim that no such reductive explanation is possible. eliminativists may reject the existence of mental properties, or at least of those corresponding to folk psychological categories such as thought and memory. mental states play an important role in various fields, including philosophy of mind, epistemology and cognitive science. in psychology, the term is used not just to refer to the individual mental states listed above but also to a more global assessment of a person's mental health. definition various competing theories have been proposed about what the essential features of all mental states are, sometimes referred to as the search for the "mark of the mental". these theories can roughly be divided into epistemic approaches, consciousness-based approaches, intentionality-based approaches and functionalism. these approaches disagree not just on how mentality is to be defined but also on which states count as mental. mental states encompass a diverse group of aspects of an entity, like this entity's beliefs, desires, intentions, or pain experiences. the different approaches often result in a satisfactory characterization of only some of them. this has prompted some philosophers to doubt that there is a unifying mark of the mental and instead see the term "mental" as referring to a cluster of loosely related ideas. mental states are usually contrasted with physical or material aspects. this contrast is commonly based on the idea that certain features of mental phenomena are not present in the material universe as described by the natural sciences and may even be incompatible with it. central to epistemic approaches is the idea that the subject has privileged epistemic access to her mental states. in this view, a state of a subject constitutes a mental state if and only if the subject has privileged access to it. it has been argued that this access is non-inferential, infallible and private. non-inferential access is insufficient as a mark of the mind if one accepts that we have non-inferential knowledge of non-mental things, for example, in regular perception or in bodily experience. it is sometimes held that knowledge of one's own mental states is infallible, i.e. that the subject cannot be wrong about having them. but while this may be true for some conscious mental states, there are various counterexamples, like unconscious mental states or conscious emotions that we don't know how to categorize. the most influential characterization of privileged access has been that it is private, i.e. that mental states are known primarily just by the subject and only through their symptoms like speech acts or other expressions by other people. an influential but not universally accepted argument against this tradition is the private language argument due to ludwig wittgenstein. he argues that mental states cannot be private because if they were, we would not be able to refer to them using public language. consciousness-based approaches hold that all mental states are either conscious themselves or stand in the right relation to conscious states. there is controversy concerning how this relation is to be characterized. one prominent early version, due to john searle, states that non-conscious states are mental if they constitute dispositions to bring about conscious states. this usually leads to a hierarchical model of the mind seeing only conscious states as independent mental phenomena, which is often a point of dispute for opponents to consciousness-based approaches. according to this line of thought, some unconscious mental states exist independently of their conscious counterparts. they have been referred to as the "deep unconscious" and figures in the cognitive sciences and psychoanalysis. but whether this counterargument is successful depends both on allowing that the deep unconscious is actually mental and on how the dependency-relation denied by the deep unconscious is to be conceived. intentionality-based approaches see intentionality, i.e. that mental states refer to objects and represent how the world is, as the mark of the mental. this circumvents various problems faced by consciousness-based approaches since we ascribe representational contents both to conscious and to unconscious states. two main arguments have been raised against this approach: that some representations, like maps, are not mental and that some mental states, like pain, are not representational. proponents of intentionality-based approaches have responded to these arguments by giving a hierarchical explanation of how non-mental representations depend on mental representations, akin to the relation between unconscious and conscious states suggested in the last paragraph, and by trying to show how apparently non-representational mental states can be characterized as representational after all. functionalist approaches define mental states in terms of their role in the causal network. for example, a pain state may be characterized as what tends to be caused by bodily injury and to cause pain expressions like moaning. behaviorism is one form of functionalism that restricts these characterizations to bodily reactions to external situations, often motivated by an attempt to avoid reference to inner or private states. other forms of functionalism are more lenient in allowing both external and internal states to characterize the causal role of mental states. phenomenal consciousness constitutes a difficulty for functionalist approaches since its intrinsic aspects are not captured by causal roles. for example, the causes and effects of pain leave out the fact that pain itself feels unpleasant. classifications of mental states there is a great variety of types of mental states, which can be classified according to various distinctions. these types include perception, belief, desire, intention, emotion and memory. many of the proposed distinctions for these types have significant overlaps and some may even be identical. sensory states involve sense impressions, which are absent in non-sensory states. propositional attitudes are mental states that have propositional contents, in contrast to non-propositional states. intentional states refer to or are about objects or states of affairs, a feature which non-intentional states lack. a mental state is conscious if it belongs to a phenomenal experience. unconscious mental states are also part of the mind but they lack this phenomenal dimension. occurrent mental states are active or causally efficacious within the owner's mind while non-occurrent or standing states exist somewhere in the back of one's mind but do not currently play an active role in any mental processes. certain mental states are rationally evaluable: they are either rational or irrational depending on whether they obey the norms of rationality. but other states are arational: they are outside the domain of rationality. a well-known classification is due to franz brentano, who distinguishes three basic categories of mental states: presentations, judgments, and phenomena of love and hate. types of mental states there is a great variety of types of mental states including perception, bodily awareness, thought, belief, desire, motivation, intention, deliberation, decision, pleasure, emotion, mood, imagination and memory. some of these types are precisely contrasted with each other while other types may overlap. perception involves the use of senses, like sight, touch, hearing, smell and taste, to acquire information about material objects and events in the external world. it contrasts with bodily awareness in this sense, which is about the internal ongoings in our body and which does not present its contents as independent objects. the objects given in perception, on the other hand, are directly (i.e. non-inferentially) presented as existing out there independently of the perceiver. perception is usually considered to be reliable but our perceptual experiences may present false information at times and can thereby mislead us. the information received in perception is often further considered in thought, in which information is mentally represented and processed. both perceptions and thoughts often result in the formation of new or the change of existing beliefs. beliefs may amount to knowledge if they are justified and true. they are non-sensory cognitive propositional attitudes that have a mind-to-world direction of fit: they represent the world as being a certain way and aim at truth. they contrast with desires, which are conative propositional attitudes that have a world-to-mind direction of fit and aim to change the world by representing how it should be. desires are closely related to agency: they motivate the agent and are thus involved in the formation of intentions. intentions are plans to which the agent is committed and which may guide actions. intention-formation is sometimes preceded by deliberation and decision, in which the advantages and disadvantages of different courses of action are considered before committing oneself to one course. it is commonly held that pleasure plays a central role in these considerations. "pleasure" refers to experience that feels good, that involves the enjoyment of something. the topic of emotions is closely intertwined with that of agency and pleasure. emotions are evaluative responses to external or internal stimuli that are associated with a feeling of pleasure or displeasure and motivate various behavioral reactions. emotions are quite similar to moods, some differences being that moods tend to arise for longer durations at a time and that moods are usually not clearly triggered by or directed at a specific event or object. imagination is even further removed from the actual world in that it represents things without aiming to show how they actually are. all the aforementioned states can leave traces in memory that make it possible to relive them at a later time in the form of episodic memory. sensation, propositional attitudes and intentionality an important distinction among mental states is between sensory and non-sensory states. sensory states involve some form of sense impressions like visual perceptions, auditory impressions or bodily pains. non-sensory states, like thought, rational intuition or the feeling of familiarity, lack sensory contents. sensory states are sometimes equated with qualitative states and contrasted with propositional attitude states. qualitative states involve qualia, which constitute the subjective feeling of having the state in question or what it is like to be in it. propositional attitudes, on the other hand, are relations a subject has to a proposition. they are usually expressed by verbs like believe, desire, fear or hope together with a that-clause. so believing that it will rain today, for example, is a propositional attitude. it has been argued that the contrast between qualitative states and propositional attitudes is misleading since there is some form of subjective feel to certain propositional states like understanding a sentence or suddenly thinking of something. this would suggest that there are also non-sensory qualitative states and some propositional attitudes may be among them. another problem with this contrast is that some states are both sensory and propositional. this is the