disjunct肯定选言 xy都可能为真 不能认为x为真,y就一定是假
consequent肯定条件 不能由结果推条件
antecedent否定前项 对条件的充分、必要性判断失误
disjunct肯定选言 xy都可能为真 不能认为x为真,y就一定是假
consequent肯定条件 不能由结果推条件
antecedent否定前项 对条件的充分、必要性判断失误
undistributed不周延
undistributed
周延:指全部的A,即all A或 no A
不周延: 指A 的一部分,并非全部,即 A, some A等
undistributed middle 指中项 在大前提和小前提都是不周延的,大项和小项无相关性
logical fallacy
逻辑谬误:
逻辑推理中的逻辑谬误
Formal fallacies
1.compound propositions
X or Y; X, therefore not Y
if X, then Y;(not) Y,therefore (not)X
三段论
前提不周言,结论周言 ✖
两个前提中中项不周言,结论大项(小项)周言 ✖
只能包含3个term
nothing等语义不明确的算2个term
Informal fallacies
九、常见的逻辑谬误(一)
Arguments: premises, inferences and conclusions. 前提,推理过程,结论
Logical Fallacy
“推理过程”错误或“前提”错误
Formal Fallacies(deductive)
valid: sound//unsound
invalid
Informal Fallacies(inductive)
Inductive Arguments are by nature Fallacious
Fallacies of Ambiguity/Relevance/Presumption
Formal: propositional fallacies 复合命题式
affriming a disjunct: X or Y; X, therefore not Y.
“小明成功既可以是因为他有才能,也可以是他人脉好。小明有才能,因此他人脉不好。”
“有才能”和“人脉好”不是完全对立的,可以同时存在。
affirming the consequent: if X, then Y; Y, therefore X.
“如果小明考试作弊,那他就能及格;现在小明及格了,说明他考试作弊了”
X不是Y的充分条件。
denying the antecedent: if X; then Y; not X, therefore not Y.
......
syllogistic fallacies 三段论式
affirmative: a. all X is Y // i: some X is Y
negative: e. no X is Y // o: some X is not Y
1.illicit affirmative: both premises are affirmative but has a negative conclusion.
e.p. All movie stars are rich.
Some rich people are mean.
Therefore, some movie stars are not mean.
2.illicit negative: 结论肯定,至少有一个否定前提。
e.p. We are not rich people.
Rich people don't care about poor people.
Therefore, we care about poor people.
3.illicit major
e.p. All X are Y
No Z are X
Therefore, no Y is Z. (大前提的Y不代表Y的全部性质,而结论的Y代表全部)
4.illicit minor
e.p. All X are Y
All X are Z
Therefore, all Z are Y. (小前提中的Z不代表Z的全部性质,而结论的Z却代表了全部)
5.undistributed middle
e.p. All cats are mammals
All dogs are mammals
Therefore, all cats are dogs. (中项mammals对于大前提cats和小前提dogs的对应部分不完全重叠,而结论把这部分完全重叠了)
6. four terms
e.p. Nothing is better than ture love.
Money is better than nothing.
Therefore, money is better than ture love. (大前提和小前提的nothing不是同一个term,这里一共有四个terms)
肯定 肯定 否定 (错误)
否定 否定 肯定 (错误)