Abstract

My dissertation aims to provide a formal semantic theory for metaphors and a computational model of that theory. A computer program, NETMET, implements the ideas presented in the dissertation. Working in a thoroughly cognitive manner, my dissertation is both rigorously mathematical and psychologically well-informed. The dissertation is scientific in method. The reasoning is primarily abductive, and each proposed hypothesis is validated against large, detailed examples from the history of philosophy and science. ;The dissertation begins by sketching a formal theory of conceptual knowledge. Conceptual knowledge is modeled as a semantic network of concepts: concepts are modeled as network nodes, propositions as structures containing such nodes. A semantic field is characterized as a cluster of densely interrelated concepts. ;The core of the dissertation is a formal theory of analogy. It is argued that analogies serve as the primary basis for the generation of metaphors. Analogies are viewed as approximate homomorphisms from a source semantic field to a target field. Constraint-satisfaction algorithms are presented for computing analogies and for transfering knowledge from the source to the target by means of an underlying analogy; particular care is taken to transfer the implicative structure of the source field. Such analogical transference produces metaphorical propositions. Rules are given for generating several syntactical forms of metaphorical utterances. ;The dissertation then proceeds to the analysis and interpretation of metaphors. Logical deep structures are provided for several syntactic forms of metaphors. For instance, copula metaphors are shown to be class-inclusion statements . A forward-chaining inference algorithm is presented that deduces literal propositions from metaphorical propositions. It is then shown how such literal entailments can be incorporated into abductive argument schema which confirm or disconfirm metaphors. In this respect, at least, metaphorical propositions are analogous to theoretical statements. Since arguments can be provided for metaphorical propositions, it is argued that they carry truth-values, and so are cognitively meaningful