谈谈词项逻辑中的几个问题
作者：余俊伟
摘要/Abstract
“一个三段论有且只有三个概念”是构成三段论的条件，不是三段论规则。对当关系中的真假不定不能看作是一简单命题用于假言三段论。词项逻辑中涉及预设的地方仅为有限量换位推理，两个全称前提推出特称结论的三段论推理及反对关系推理和下反对关系推理；所需预设均为：主项存在。从操作层面上看周延规则不是普遍适用的；从深层次来看，如考虑到预设那，那么周延规则是普遍适用的。
That a syllogism includes exactly three terms should not be viewed as a rule of a syllogism but a necessary condition for forming a syllogism. Undefined truth-values in the square of opposition cannot be used as a simple proposition in hypothetical syllogisms vaguely. The existential import is needed only when we make the following three kinds of inferences in categorical logic: conversion by limitation, the syllogisms with existential conclusions and two universal premises, and the inferences of contrariety and subcontrariety. The import is that the subject class is not empty. For convenience we can think the rule on distribution is local. However we can view it universal when considering more factors.
