古德曼的共同支撐理論述評

The main idea of Goodman's cotenablity theory is that a subjunctive conditional ”φ＞ψ” is true iff ”φ”, in conjunction with a set S of true sentences and some natural laws, entails ”ψ”. There are two obvious difficulties for such a theory: (a) to give an account of what these sets of true sentences are like? and (b) to explain what a natural law is? I focus mainly on the first difficulty and have done several things in the present paper. First, I give an explanation of how this difficulty arises, special attention being to the circularity problem in defining 'cotenability'. Second, I discuss and refute several suggestions aiming at giving a solution to the problem of circularity and set aside a few objections to cotenability theory based on misunderstanding. Third, by distinguishing the assertibility of a statement and its truth-condition, I propose a way which, according to my opinion, might be useful in solving the problem of circularity. Fourth, I briefly compare Goodman's cotenability theory and those currently more popular possible-world theories for subjunctive conditionals and point out the main merits of the latter. Finally, I briefly discuss the problem of explaining what a natural law is for a cotenability theorist. Appendix is a more detailed and semi-formal presentation of Goodman's discussion in his (1947).