section_path: Theories of the nature of mind
section_name: Theories of the nature of mind
paragraph_text: Theories of the nature of mind
  
  Theories of the nature of mind aim to determine what all mental states have in common. They seek to discover the "mark of the mental", that is, the criteria that distinguish mental from non-mental phenomena. Epistemic criteria say that the unique feature of mental states is how people know about them. For example, if a person has a toothache, they have direct or non-inferential knowledge that they are in pain. But they do not have this kind of knowledge of the physical causes of the pain and may have to consult external evidence through visual inspection or a visit to the dentist. Another feature commonly ascribed to mental states is that they are private, meaning that others do not have this kind of direct access to a person's mental state and have to infer it from other observations, like the pain behavior of the person with the toothache. Some philosophers claim that knowledge of some or all mental states is infallible, for instance, that a person cannot be mistaken about whether they are in pain.
  
  A related view states that all mental states are either conscious or accessible to consciousness. According to this view, when a person actively remembers the fact that the Eiffel Tower is in Paris then this state is mental because it is part of consciousness; when the person does not think about it, this belief is still a mental state because the person could bring it to consciousness by thinking about it. This view denies the existence of a "deep unconsciousness", that is, unconscious mental states that cannot in principle become conscious.
  
  Another theory says that intentionality is the mark of the mental. A state is intentional if it refers to or represents something. For example, if a person perceives a piano or thinks about it then the mental state is intentional because it refers to a piano. This view distinguishes between original and derivative intentionality. Mental states have original intentionality while some non-mental phenomena have derivative intentionality. For instance, the word piano and a picture of a piano are intentional in a derivative sense: they do not directly refer to a piano but if a person looks at them, they may evoke in this person a mental state that refers to a piano. Philosophers who disagree that all mental states are intentional cite examples such as itches, tickles, and pains as possible exceptions.
  
  According to behaviorism, mental states are dispositions to engage in certain publicly observable behavior as a reaction to particular external stimuli. This view implies that mental phenomena are not private internal states but are accessible to empirical observation like regular physical phenomena. Functionalism agrees that mental states do not depend on the exact internal constitution of the mind and characterizes them instead in regard to their functional role. Unlike behaviorism, this role is not limited to behavioral patterns but includes other factors as well. For example, part of the functional role of pain is given by its relation to bodily injury and its tendency to cause behavioral patterns like moaning and other mental states, like a desire to stop the pain. Computationalism, a similar theory prominent in cognitive science, defines minds in terms of cognitions and computations as information processors.
  
  Theories under the umbrella of externalism emphasize the mind's dependency on the environment. According to this view, mental states and their contents are at least partially determined by external circumstances. For example, some forms of content externalism hold that it can depend on external circumstances whether a belief refers to one object or another. The extended mind thesis states that external circumstances not only affect the mind but are part of it, like a diary or a calculator extend the mind's capacity to store and process information. The closely related view of enactivism holds that mental processes involve an interaction between organism and environment.