※ 引述《realove (realove)》之銘言： : 你問這個問題還蠻有趣滴 : 我不知道I會怎麼回答 但ㄟ : 我說一下我個人的意見 : 我想I之前 就有強調兩種意義的possible world : 一種是david lewis講的possible world : (我對lewis沒有很熟 講錯了請糾正) : 這種possible world的集合 包括了actual world Yes, and Lewis said all possible worlds (all members in W) are concrete. : 另一種是kripke講的possible world : 這種意義下的possible world是相對於actual world而言 它實際上不存在 卻有可能存在 : 如假如有一個世界的狀態是 Aristotle不是柏拉圖的學生 那這只是一個可以被想像的 : (conceivalbe)possible world 而不是actual world : 所以對kripke而言 possible world的集合裡並不包括actual world No, Kripke semantics says nothing about actual world. and there is no outstanding reason suppose actual world is different from other possible worlds semantically, since we can handle all relevant issues in modal logic. Simplification is one of our concerns. I will show you, if actual world is different from other possible worlds, then its model will look like what. Suppose I can do that. Model-theoratically, If Kripke supposed actual world is not in W, there will be a serious problem in the original model. The problem is that we get some objects the model cant handle. The original Kripke's model have to be modified. Intutively, we can say that actual world (wa) itself is a set , and has its own relations, so that our new model for wa becomes <Wa,Ra,v> , called Mwa. But soon we encounter a crux, since wa is different from its friends - others possible world. Between them, there must have at least a relation(?) between them, or we cant draw a clear line to specify them. Models for other possible worlds would be <Wo,Ro,v>, called Mom. The most important target now is try to find the diagram between Mom & Mwa, so that we can get a "good" semantics for this topic. Forgive my ignorance and foolish, the easiest way is to say this diagram is isomorphic. For a reson(not quiet strickly), its very unwisdom to divde similar realtions into Ro and Ra. Now we have a new model functions as K, very likely in practice. So, we use the orignal K-semantics again. Something tricky, isnt it? --

※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.112.143.99 ※ 編輯: aletheia 來自: 140.112.143.99 (10/19 16:58)