对休谟可设想性论题的哲学反思——以必然后验命题为视角

Philosophical Reflection on Hume's Conceivability Thesis——On the Perspective of Necessary A Posteriori Propositions

休谟的可设想性论题在"可设想性"和"可能性"之间建立起了逻辑连接,进而成为人们获取模态知识的主要途径。遵此论题,一个陈述的可设想性蕴含其可能性。克里普克在对后验必然命题的存在进行论证时却破坏了二者之间的关联,他主张有些陈述是可设想的,但不可能成立。实际上,必然后验命题与休谟的可设想性论题并不冲突,形而上学的必然性不等同于逻辑上的必然性。但必然后验命题的存在说明,休谟的可设想论题作为获取模态知识的主要路径是不够精细的。有必要对"可设想性"与"可能性"以及二者之间的关系进行细致分析,由此可以获得的教益是:第一,人们的设想行为会受不同规律、法则的约束,从而形成不同的可设想性;第二,根据不同的规律,可以区分出不同类型的可能世界,进而区分出不同层面的必然性和可能性;第三,不同的可设想性和不同类型的可能性之间存在着对应关系。

Conceivability Thesis,put forward by David Hume,linked a logical connection between conceivability and possibility.According to this thesis,the conceivability of a statement implies its possibility.While arguing for the existence of Necessary A Posteriori Propositions,Saul Kripke suggested that some statements are conceivable but not possible,and thus destroyed this connection.In fact,Necessary A Posteriori Propositions are compatible with Hume’s Conceivability Thesis,metaphysical necessities are not equivalent to logical necessities.However,the cases of Necessary A Posteriori Propositions show clearly that Hume’s Conceivability Thesis as the main access to getting modal knowledge is ill-equipped.It’s necessary to make analysis of conceivability and possibility,as well as the relationship between them,and we can draw the moral finally that,firstly,our behavior of conceiving restricted by defferent laws or rules could lead to defferent conceivabilities;Secondly,according to different laws,different types of possible worlds can be distinguished,and the necessities and possibilities of different levels can be distinguished.Third,there is a correspondence between different conceivablities and different types of possibilities.