Monday, October 09, 2006

美人美食 邏輯考究

與朋友聊天,講起在香港找了老半天,
還是找不到日本的蛋糕(ケーキ)與巴菲(パフェ)等甜點。
説來,最近沒有寫美人美食的環節啦,
好像沒有去採訪什麽好美食。
得出原因如下:


吃Cake得有個美人
最近沒有美人
---------
最近沒有吃Cake


[邏輯的表記?]
{(p->q) & ~p } -> ~q

怎麽看都好像是謬誤 fallacy ~logically invalid是也~(茶)
(大一邏輯都還給李生啦 XD) 有興趣的人去查邏輯書 (逃走

這個世界只有
正斷律 {(p->q) & p } -> q
逆斷律 {(p->q) & ~q} -> ~p
所以問題是
如果 有美人才有Cake吃,沒有美人,則不能推論出我不能吃Cake?
奇妙?怎麽也覺得一塌糊塗啦 XD
以上,不負責的邏輯推論完結。


某朋友卻認爲應該如此:


吃Cake得有個美人
吃了Cake
--------
得個美人


聼完立刻倒地
真的好似好有道理啊!!!! 而且實用的說?
有興趣的讀者拿來當邏輯練習,
看看這個神奇的推論有什麽問題。

2 comments:

ka said...

吃Cake得有個美人
吃了Cake
--------
得個美人


完全推論不出啊……
怎樣推出來的?
你說"推倒"倒是可以想像一下……

Anonymous said...

吃Cake得有個美人
吃了Cake
--------
得個美人

The logical conclusion should be "有個美人", not "得個美人."

By replacing the word "有" with "得", your friend is altering the logic. If I translate this false argument to English, it would look like this.

1. One can eat a cake ONLY IF there's a beauty.
2. One ate a cake.
______________________________
Conclusion: ONLY IF a beauty.

It doesn't make sense.

The meaning of "得" has also been changed. In the premise, it was intended to mean "must have" or "require." In the conclusion, however, the meaning of "得" was changed to "gain" or "acquire."
This problem came up because your friend manipulated the double meaning of "得" in Chinese.

Sorry for taking this problem seriously. You probably know the answer already, but I'm bored because I'm stuck in class and have too much time on my hand :P