It can be argued that every new model is developed from an existing model (Lakoff & Johnson, 1980). The reduction ad absurdum aspect of this statement (i.e. where did the first model of a phenomenon come from?) offers wide scope for philosophical debate. The nature of and relationship between metaphor and analogy, the keys to the development of new models, is much disputed by linguists (Black, 1979). However, in broad terms, a metaphor is the temporary assumption that one thing is another thing. Thus ‘the sun is a furnace.’ The issue then is to decide the extent to which this identity is justified. Analogy is where a thing is said to be like another thing. An analysis of ‘the sun is like a furnace’ enables those aspects of a furnace that ‘map onto’ the sun to be used in a description of the latter. Hesse (1966) identified three aspects of any ‘source’ (e.g., a furnace) that is used to describe the target (e.g., ‘the sun’). There is the positive analog, which could properly be used in the analogy (the model). There is the negative analog, which could not be used in the model. And, perplexing for all students, the neutral analog, where it was not clear whether those parts can be ‘translated’ into the model or not.
Metaphor and analogy sit within the complex of the verbal linguistic devices used in science and elsewhere. The verbal mode can be the presentation of the model as a structure in its own right i.e. a description of the entities of which it is thought to consist and of the relationships between them. However, it is often the case that a verbal presentation seeks to explain the model i.e. to show how and why it was produced. This latter type of verbal presentation is thus concerned with the identification of similarities between something that is already understood and something that has to be understood with the use of analogy. However, ‘similarity’ is