Theory which treats declarative sentences (as against commands and so on) as pictures of facts (if true) or possible facts (otherwise). A notable example of the theory is Tractates (1921) by Ludwig Wittgenstein (1889-1951).
Each element in the sentence (bar certain connectives and so on) stands for something, be it an object or a quality or a relation, and so on; and the connectives and the way the words are put together correspond to the way the objects and qualities and so on are related in the envisaged situation.
The theory is thus a form of correspondence or relational theories of meaning analogous to naming theories of meaning for Singular terms. One objection is that it does not seem to cater for the difference between merely picturing a scene and stating that that scene is part of reality.
E Daitz, ‘The Picture Theory of Meaning’, Mind (1953); reprinted in A Flew, ed., Essays in Conceptual Analysis (1956)
Idea theory of meaning
The idea theory of meaning (also ideational theory of meaning), most commonly associated with the British empiricist John Locke, claims that meanings are mental representations provoked by signs.
The term “ideas” is used to refer to either mental representations, or to mental activity in general. Those who seek an explanation for meaning in the former sort of account endorse a stronger sort of idea theory of mind than the latter. Those who seek an explanation for meaning in the former sort of account endorse a stronger sort of idea theory of meaning than the latter.
Each idea is understood to be necessarily about something external and/or internal, real or imaginary. For example, in contrast to the abstract meaning of the universal “dog”, the referent “this dog” may mean a particular real life chihuahua. In both cases, the word is about something, but in the former it is about the class of dogs as generally understood, while in the latter it is about a very real and particular dog in the real world.
John Locke considered all ideas to be both imaginable objects of sensation and the very unimaginable objects of reflection. He said in his Essay Concerning Human Understanding that words are used both as signs for ideas and also to signify a lack of certain ideas. David Hume held that thoughts were kinds of imaginable entities: his Enquiry Concerning Human Understanding, section 2. He argued that any words that could not call upon any past experience were without meaning.
In contrast to Locke and Hume, George Berkeley and Ludwig Wittgenstein held that ideas alone are unable to account for the different variations within a general meaning. For example, any hypothetical image of the meaning of “dog” has to include such varied images as a chihuahua, a pug, and a black Labrador; and this seems impossible to imagine, since all of those particular breeds look very different from one another. Another way to see this point is to question why it is that, if we have an image of a specific type of dog (say of a chihuahua), it should be entitled to represent the entire concept.
Another criticism is that some meaningful words, known as non-lexical items, don’t have any meaningfully associated image. For example, the word “the” has a meaning, but one would be hard-pressed to find a mental representation that fits it. Still another objection lies in the observation that certain linguistic items name something in the real world, and are meaningful, yet which we have no mental representations to deal with. For instance, it is not known what Newton’s father looked like, yet the phrase “Newton’s father” still has meaning.
Another problem is that of composition—that it is difficult to explain how words and phrases combine into sentences if only ideas are involved in meaning.
Eleanor Rosch and George Lakoff have advanced a theory of “prototypes” which suggests that many lexical categories, at least on the face of things, have “radial structures”. That is to say, there are some ideal member(s) in the category that seem to represent the category better than other members. For example, the category of “birds” may feature the robin as the prototype, or the ideal kind of bird. With experience, subjects might come to evaluate membership in the category of “bird” by comparing candidate members to the prototype and evaluating for similarities. So, for example, a penguin or an ostrich would sit at the fringe of the meaning of “bird”, because a penguin is unlike a robin.
Intimately related to these researches is the notion of a psychologically basic level, which is both the first level named and understood by children, and “the highest level at which a single mental image can reflect the entire category” (Lakoff 1987:46). The “basic level” of cognition is understood by Lakoff as crucially drawing upon “image-schemas” along with various other cognitive processes.
Philosophers Ned Block, Gilbert Harman and Hartry Field, and cognitive scientists G. Miller and P. Johnson-Laird say that the meaning of a term can be found by investigating its role in relation to other concepts and mental states. They endorse a “conceptual role semantics”. Those proponents of this view who understand meanings to be exhausted by the content of mental states can be said to endorse “one-factor” accounts of conceptual role semantics and thus to fit within the tradition of idea theories.