Abstract

The thesis develops and argues for a version of realism about micro entities postulated by scientific theories. It begins with analyses of the concepts of reality, observation, interaction, causality and reasonableness, which are crucial in the modern realism debate. In this way, it is found that, within the debate, a move from the acceptance of the causal role of an entity to the acceptance of its reality is legitimated. Hence "good reasons" for accepting the reality of the entity are those that indicate that its causal relevance to some other objects has been conceptually and experimentally identified. The acceptance is reasonable in the sense that it both is the best choice and is relative, open and critical. Given this recognition, the constituents of "good reasons" for identifying a postulated entity's causal relevance are sought. Such logical attempts as hypothetico-deductivism, Glymour's bootstrapping theory and Sylvan's programme for relevance logics of cause are demonstrated to be incapable of identifying the causal relevance. Hence the "experimental approach" is preferred and developed. An account of good reasons based on a cause identification condition, which consists of a model constituent and an experiment constituent, is proposed, clarified and defended by case studies of models and experiments in elementary particle physics and molecular biology. These experiments are shown for the first time to have a special tree-structure, which reflects a synthesis of their self-checking and -correcting mechanisms and which makes them manipulations of the postulated entity. It is argued that through the tree structure scientists' belief in the reality of DNA molecules is rooted in the nature of the technology used to manipulate them. Finally, with a comparative case study of the neutrino and the ether, the challenge by Laudan for realism is met and the adequacy of the account of good reasons is further proved. The thesis has philosophically accounted for the reasonableness of scientific belief in the reality of the micro-entity