命题的一个新定义与命题的同一性问题

A new definition of proposition and the identity problem of propositions

命题曾被定义为某些句子,但句子没有固定的真值。命题曾被定义为句子的意义,但"意义"这个概念并不比"命题"更清晰。还原论把命题定义为一种由可能世界、可能的个体等组成的集合论性的构造物,但这种理论意味着全部的逻辑真理表达的是同一个命题。命题曾被定义为是一些态度(如相信)的对象和真值的承担者;就是说,命题是由它与其他对象(如人,真值)的关系来定义的;这种定义使人们有理由怀疑命题是否真正存在,抑或是态度主体(人)的一种幻觉?命题的内容可以千变万化,但命题的内容却有共同的形式,不仅命题逻辑、一阶逻辑所表达的命题,而且二阶逻辑等高阶逻辑、非经典逻辑的命题,都能纳入这种形式。根据这一点我们提出了一个新的对命题的定义。这样定义的"命题"概念更加清晰,能让我们解决命题的同一性问题。

Proposition has once been defined as a kind of sentence,but a sentence has no fixed truth value.Proposition has once been defined as the meaning of a sentence,but the concept“meaning”is not clearer than the concept“proposition”.Re-ductionism reduces propositions to set-theoretical constructs ultimately built up from the possible world or possible particulars, but it implies that all logical truths are different expressions of the same proposition.Proposition has once been defined as the object of some attitudes （e.g.believing）and the bearer of truth and falsity;i.e.,it is defined by its relation with other things （human beings,truth value）.This leaves room for doubting whether there are really propositions or they are only halluci-nations of the subject （people）of the attitude.The contents of different propositions can be much different,but yet they share a general form.Not only the propositions of propositional logic and first-order logic,but also the propositions of second-order logic,higher order logics and non-classical logics can be categorized into this form.With these we can give a new definition of proposition.“Proposition”so defined is a clearer concept.It enables us to solve the identity problem of propositions.