點解邏輯學唔係必修？

To younger philosophers in 1973, Ayer appeared quite old-fashioned philosophically. So too, though to a lesser extent, did Strawson. The underlying reason was in large part their relation to modern formal logic in philosophy. Officially, Ayer was for it and Strawson against it, but neither of them knew much about it. They had received their philosophical education at a time when such logic did not loom large in Oxford... The effect of Ayer and Strawson’s lack of facility with modern formal logic was that they were poorly placed to deal with the new wave of philosophy of language sweeping across the Atlantic, led by Kripke and Lewis...


日常用語學派 直頭係俾 formal semantics 取代:

Strawson was much more of a philosopher of language than Ayer, but even his perception of new wave philosophy of language was distorted by the old-fashioned lens of an exaggerated contrast between, in effect, ordinary language philosophy attentive to speakers’ actual use of natural language in all its complexity and ideal language philosophy trying to project the simple logical structure of a formal language onto natural language, in abstraction from its speakers, with Procrustean effect (Strawson 1971). What he never properly appreciated was the new wave conception of the two projects as mutually complementary rather than in competition, so that interpreting a natural language in terms of a comparatively simple formal truth-conditional semantics would make the best sense of the complexities of speakers’ actual use of the language.

大學sit哲學系既堂，個教授叫啲哲學major既學生，可以用日常語言表達就盡量用日常語言，避免用邏輯語言。因為分析哲學其中一個目的係促進公共理解，最好連高中生都睇得明，無謂製造啲不必要既障礙。

唔知點解我覺得佢講呢番話嗰陣好型

當然呢幾段野係 Williamson 寫，佢一家之言咁解
唔好盡信

當然 如果你搞政治哲學 applied ethics 呢d
梗係要公眾理解
但好多哲學問題都唔洗公眾明

而且好多複雜嘅哲學問題
有堆哲學家以為日常用語 ＋ classical logic 都搞得掂 其實不然

我都好撚希望有人可以用日常語言解釋到啲乜鳩k logic, t logic, s4, s5比我聽 文科生見到都想死

我中學都文科 其實唔難

modal propositional logic 嘅 model 咪一個<W, R, V>結構
1) W 咪一個 possible worlds 嘅集合，呢度好正路
2) V 咪分配返 proposition 係每個 world 嘅 truth-value
等同命題邏輯嘅 truth assignment咁解 但而家係相對 world 來講

即係本身你係 propositional logic 只會話 p is true
而家會話 p is true at w
咁 V 係一條 function，你 input 某個命題 p 同某個 world , 佢會 output 個 truth value咁

3) 可能你唔明白嘅係 R
R 係accessibility relation ，係 worlds 之間嘅關係
如果你諗唔到 點解要有個 R，唔洗用直覺諗太多架啦
總之而家就係，有興趣 worlds 之間嘅關係

4) 咩 K, T, S4, S5 咪分別在於個 R 有唔同關係
K 咪冇任何性質加諸於 R
T 咪規定 R 係 reflexive, 即係任何 worlds w, 自己都同自己相通
(for all w in W, Rww)

S4 咪 reflexive + transitive
(transitive：如果 w1, w2 有R關係， w2, w3 有 R 關係，則 w1 同 w3 有 R 關係）

S5 入面，R 咪規定係 reflexive, symmetric, transitive,
有齊呢 3個性質，即係一個 equivalance 嘅關係
咪即係個個 world 都相通

咁godel係點論證上帝存在？

由於啲worlds係相通，所以當我話
“上帝可能存在”

即係“上帝喺至少一個possible world存在”

由於啲worlds相通，所以上帝必然存在？

我好似理解得麻麻地

先唔講有冇用
就算呢科真係香港變必修
成件事都會扭曲哂學考試技巧果d
自然d人都唔會點去思考d理論點套用返係現實生活
本身邏輯學就已經係個幾理論性既科
而係香港 真正想令學生張理論套用係現實世界既科 理想中就係通識科，點知又係扭曲哂，睇佢本pastpaper d marking scheme都發現邏輯亂9咁黎
我自己year1讀完discrete math 當時冇咩心機讀都係諗住求其合格就算，所以讀都唔會真係去研究同思考d邏輯，到最後都大把skills可以比你秒速pick up返d野 根本係香港冇讀同讀左係差唔多

即係如果我話「太陽即是月亮是1+1唔等於2嘅必要條件」係唔可以咁講，但係「If 1+1唔等於2，then 太陽即是月亮」係符合邏輯？

無錯，喺邏輯語言入面既if x, then y.
x同y係唔需要有因果關係。

如果要強調“if x, then y”，個x同y有因果關係，咁就要引入 必然 同 偶然 兩個算子，喺邏輯語言入面就係diamond同box符號

因為女人多數讀商 將來做你女上司

其實我想知點為之因果關係呢？
例如話「Y是X的必要條件」，噉係咪就代表X同Y一定有因果關係？
又例如話「如果X，必然出Y」，噉係咪就代表X同Y一定有因果關係？
咁如果話「If X, then Y」，噉只係代表X同Y有機會有因果關係，亦都有機會係無因果關係？

問題係我點樣去判斷嗰兩句嘢有冇因果關係呢？

例如我話
「if 打工，then 有人工」
「if 1+1唔等於2，then 太陽即是月亮」

上面嗰句以常識嚟講係因果關係，因為打完工，所以就有人工
但我點判斷1+1唔等於2同太陽即是月亮係無因果關係呢？

但係點解通常啲人會寫，if A, then B就等於或者代表B就是A的必要條件，A就是B的充分條件？

重有一樣嘢，如果我話「if 1+1唔等於2，then 1+1等於2」會有咩事發生？

有個哲學佬叫david hume，佢比過因果關係既三個條件
1.時間空間上相鄰（因同果唔好距離太遠）
2.因一定先於果（時間上）
3.恒常既連結 （次次都一樣無例外）

咁當然其他哲學家亦有唔同睇法。有啲哲學家認為有因果關係唔代表有必然關係

唔識，等其他人答

咁平時我講if A, then B，咁應該要點樣解釋好呢？
上面有位巴打話唔可以講話「A出現，B必然會出現」，又唔可以講絕對話「B是A的必要條件」，又話正常噉諗係無問題，但又唔可以咁強調，我都搞到又啲亂

教識妳咪 差輪廚 政府

會錯囉，因為假如前半句正確，咁後半句一定係錯。前啱後錯，所以呢個條件句係錯。但更詳細既唔知點答你

因為喺日常交談既條件句入面，a同b往往係有因果關係。大家都習慣左。其實無乜必要將邏輯語言既語用規則搬落日常語言，畢竟係兩種語言

但係點解通常啲人會寫，「if A, then B」 就等於或者代表 「B就是A的必要條件，A就是B的充分條件」？

呢樣嘢係咪絕對啱嘅？

https://lihkg.com/thread/846642/page/1

睇下個post真係經典
第3個reply都咁多人正評