作者ntddt (哀便毛)
看板logic
标题[请益]进阶三段逻辑题
时间Tue Apr 7 20:18:41 2009
因不知如何search这题目是否在文章内文问过, 所以先问大家, ^^"
希望诸位高手指出我的盲点, Thanks!
前提:
1. Some Little Dog are not Mean Animals
2. All Dogs are Animals
结论:
Some dogs are mean
请问这样推论是否合理?
网路上正确解答是 "不合理"
理由是:
Minimal missing premise:
It exists something that is dog and mean or dog and not animal
但我想法比较单纯, 我觉得是"合理"原因如下:
假设有以下几类样本, 读法是 e.g.
1: Little + Dog + Not Mean + Animal
2: Little + Dog + Mean + Not Animal
...
| L | D | M | A
------------------------
1 | O | O | X | O
2 | O | O | O | X
3 | O | O | X | X
4 | O | O | O | O
前提2成立: 样本2,3不存在
前提1成立: 样本1,4同时存在,
因为只存在
样本1的话, 前提应该是All Little Dog are not Mean Animal
样本4的话, 前提应该是All Little Dog are Mean Animal
所以1,4同时存在, 表示Some Little Dog are Mean Animal->Some Dog are Mean
请指正, 谢谢
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※ 编辑: ntddt 来自: 203.73.48.17 (04/07 20:19)
※ 编辑: ntddt 来自: 203.73.48.17 (04/07 20:19)
1F：推 ksmrt0123:考虑一种情形: all dogs are animals and not mean 04/08 00:49
2F：→ ksmrt0123:符合前题(1)(2), 可看出结论错误 04/08 00:50
3F：→ ntddt:如果是All dogs are animal are not mean, 那条件some就有 04/08 01:34
4F：→ ntddt:问题, 应该是All little dog are not mean animal ? 04/08 01:34
5F：推 teves:这牵扯到some的定义,在英文中some可以是 04/08 10:35
6F：→ teves:more than one, possibly all 04/08 10:36
7F：→ teves:也可以是not all, possibly none 04/08 10:36
8F：→ teves:不过既然是逻辑,我想应该比较可能是particular quantifier 04/08 10:37
9F：→ teves:也就是existentail quantifier "∃" 04/08 10:41
10F：→ teves:也就是存在至少一个,可能全部的意思 04/08 10:42
11F：→ teves:抱歉上面more that one有点错,应该是at least one 04/08 10:43
12F：推 ksmrt0123:---------------------------------------------------- 04/08 13:26
13F：→ ksmrt0123:查了字典, some有not all的意思的用法是 some of 04/08 13:27
14F：→ ksmrt0123:If you refer to some of the people or things in a 04/08 13:28
15F：→ ksmrt0123:group, you mean a few of them but not all of them. 04/08 13:28
16F：→ ksmrt0123:If you refer to some of a particular thing, you mean 04/08 13:29
17F：→ ksmrt0123:a part of it but not all of it. 04/08 13:29
18F：→ ksmrt0123:...每次都从讨论逻辑都变成讨论语言... 04/08 13:32
19F：→ ksmrt0123:---------------------------------------------------- 04/08 13:33
20F：推 MathTurtle:印象中有些some of好像一定要用到second order才能表示 04/08 16:50
21F：→ ntddt:我猜逻辑上some应该是1~All, Only some才是1~(All-1), 那就 04/08 19:50
22F：→ ntddt:可以解释这题目了. All A are B情况下, Some A are B成立 04/08 19:51