Mental Representation

Concerning mental content, one hypothesis is that the content of a representation is determined by the role it plays in a person's overall system of mental representations. As an analogy, consider chess pieces: the difference between a knight and a bishop consists in the fact they have distinctive ways of moving—they play different roles in the game. Similarly, mental representations with distinct contents differ in the types of inferences they invite: believing that Tom is tall leads to different conclusions than does believing he is handsome, and each of these beliefs will be the result of different sets of prior beliefs. Perhaps, then, these differences in roles are constitutive of the content of those beliefs.

One difficulty such theories face is that, because it is unlikely that any two people will share precisely the same network of representations, no two people possess beliefs with the same contents—a counterintuitive result. Additionally, the relationship between playing a certain role and "standing for" something is unclear. How do representations come to relate to things in the external world?

An alternative theory makes more of the representation-world relationship, proposing that the content of a representation is determined by its resemblance to things in the world. Just a painting of Napoléon Bonaparte represents Napoléon (and not Abraham Lincoln) because it looks like Napoléon (and not Lincoln), a mental representation has the content it does because it resembles that which it represents. This proposal also faces challenges. For example, if for a representation to resemble something is to picture, how can abstract entities (e.g., "justice") be represented?

A descendant of the resemblance theory hypothesizes that the causal relations a representation has with the environment fix the content of that mental representation. According to a simple version of this theory, content is determined by the things that normally cause that representation to occur. For example, the "eagle" concept has the content it has because eagles (as opposed to other types of animals) cause one to think about eagles, that is, to instantiate that representation.

Despite obvious flaws in this simple theory (e.g., if a duck causes someone to think about eagles, then ducks are part of the content of the "eagle" representation), more elaborate causal theories of content remain popular.