选言命题辨析

On Disjunctive Proposition

选言命题是指一种断定它的支命题至少一个为真并且它们在部分情况下虽然可以同真但又非必须同真的复合命题。在逻辑史上,选言命题最初仅指不相容选言命题,直至十三世纪后期才被广泛的用作既包括不相容选言命题又包括相容选言命题。有趣的是,由于相容选言命题现在通常被简称为选言命题,所以选言命题又反过来通常仅指相容选言命题。如果一个不相容选言命题包含的选言支多于两个,那么按照真值表的通常做法,该不相容选言命题在真值表中的赋值就会出现不符合其逻辑特征的情况。如果不相容选言命题联结词视为一个二元联结词,那么就会出现这种问题。相反,如果不相容选言命题联结词被视为一个多元联结词,那么这种问题就可以得到彻底解决。

A disjunctive proposition is a compound proposition which declares that at least one of its branches is true and although the branches may be true at the same time in some situation but they do not have to be so.In the history of logic,the disjunctive proposition only refers to incompatible disjunctive proposi tion at first.Not until the late 13th century were they widely used to include both incompatible and compatible disjunctive propositions.Interestingly,compatible disjunctive propositions are now called disjunctive proposi tions for short usually,so the disjunctive proposition in turns usually just means the compatible disjunctive proposition only.If an incompatible disjunctive proposition contains more than two branches,then according to the common use in truth table,the assignment value of the incompatible disjunctive proposition in the truth table will appear to be conflicted with the logical feature of the proposition.This problem arises when the con nectives of an incompatible disjunctive propositional is treated as a 2-place one,while it can be solved com pletely when the connective treated as a multiple place one.