This study in cognitive science brings together traditional philosophical questions about meaning and meaning relationships with recent findings in cognitive psychology, neurology, ethno-linguistics, and new methods of semantic research. Part 1 is a query into the nature of meaning relations as projected in the notion of conceptual and semantic fields. Words related in meaning are organized in a semantic field. Theoretical as well as methodological questions about semantic fields are dealt with in the light of new findings about conceptual networks, memory structure, retrieval mechanisms, and the modularity of language as revealed by differences of age, status, sex, culture, etc. It is suggested that a firm basis exists for further research in relations in various semantic fields, viewing these fields as the actual realization of cognitive networks. Part 2 details the obstacles as well as the benefits gained in conducting research on a semantic field of a difficult philosophical concept such as ‘similarity’. Verbs, nouns, adjectives, prepositions, and idiomatic expressions of similarity and related notions (mainly in Hebrew) are examined through their semantic relations and their respective roles in the semantic field. Two main conclusions result from this investigation: a) ‘Similarity’ is a bundle of relations rather than a unitary concept. It gathers under one roof subtypes of similarity such as: analogy and comparison, parallelism, duplication, part-whole relations, copy, forgery, and mistaken identification. Each subtype has its own logical characteristics. b) The mechanism that gathers these subtypes of similarity under one concept, ‘similarity’, is based on a quasi-contradiction or tension between unity and plurality, between precision (‘the very image’) and loose ends (‘images’). These two characteristics of ‘similarity’ account for its aptness to perform its cognitive function as an adjuster, a liaison between newly acquired, unlabeled information and a whole body of structured knowledge. Part 3 sets forth further applications of the semantic field method. Alternations of closely related words and expressions in the field shed new light on the choice of words and the issue of selectional restriction in meaning. Alternation of related discourse metaphors points out their nature as rule-governed devices. Several rules of meaning render such metaphors understandable and meaningful. This study is an initial step toward a theory of the logical-semantic basis of metaphor. The complete book shows what is gained by combining traditional philosophical and linguistic questions with modern research methods and their findings.