戴維森論思想的客觀性

Abstract

依照戴維森的說法，知識有三種：自我知識、他心知識、與有關外在世界的知識。一方面，這三種知識互相獨立，也就是說，沒有其中一種知識可以被還原成另一種或是另兩種知識；另一方面，如果我們有任何知識的話，我們就會同時擁有這三種知識，而不可能只有其中一種或兩種而已。但是這三種知識都是客觀的。戴維森在他的三角測量(Triangulation)理論中解釋為什麼思想是客觀的。粗略地說，三角測量是由兩個人與他們共享的世界所組成，他們透過對外在世界的觀察與對對方反應的觀察來解釋對方所講的話。可是戴維森的三角測量理論主要是關於對外在世界的知識與他心知識，至於自我知識的客觀性要如何用三角測量理論來解釋則不明顯。其中最大的因難是對於自我知識，似乎缺少了三角測量理論中所要求的兩人所共享的遠因(distal cause)，而這個遠因是三角測量理論不可或缺的。 本文的目的就是嘗試找出對自我知識的遠因，從而透過三角測量理論解釋自我知識的客觀性。如果成功的話，將會使戴維森對思想的客觀性的解釋更加完整。第一章檢視Frege與Russell對思想的客觀性的解釋，以及他們各自的解釋的失敗之處。Frege雖然想利用語言的客觀性來保障思想的客觀性，但是他並沒有解釋這是如何做到的。Russell則想利用真理的符應理論來說明思想/命題的客觀性，但是從戴維森的彈弓論證(slingshot argument)來看，真理的符應理論並沒有解釋能力；而且Russell的理論預設了意義的檢證理論，而這個理論是無法成功的。 第二章檢視Quine如何利用觀察語句指涉到外在世界的方式來解釋思想的客觀性。但是這個進路預設了自然語言中有很明確的觀察語句與非觀察語句的區分，而且觀察語句同時是作為有關外在世界的知識的證據。根據戴維森的論證，這樣的預設卻無法回應有關外在世界的知識的懷疑論。 在第三章我解釋戴維森如何以Tarski的約定T來建立一個經驗的真理理論，並解釋這樣的真理理論能作為一種意義理論。這章的後半說明戴維森利用徹底解釋理論來解釋信念的性質，從而回應懷疑論。 第四章說明戴維森如何用三角測量理論來說明思想的客觀性，以及論證對自我知識而言，也有適當的遠因，故三角測量理論亦能解釋自我知識的客觀性。

According to Davidson, there are three varieties of knowledge, or three ‘different mode of access to reality’: knowledge of one’s own mind, knowledge of other minds, and knowledge about the world. On the one hand, all three varieties of knowledge are mutually independent, i.e., no one of them could be reduced to other two or another one of them; on the other hand, all three of them are essential for us to have any knowledge, that is, no knowledge would be possible without any one of them. Nevertheless, there is at least one thing these three varieties of knowledge are in common: objectivity. The objectivity of thought is explained in Davidson’s thesis of triangulation. Roughly speaking, triangulation is a process consists of two persons and a world they share, each person knows what the other says mean through observing the world they shared and the other’s reaction to it. However, his account concerns mainly knowledge about external world, and knowledge about other minds. It is not obvious how self-knowledge could be explained by triangulation. The problem is that regarding to self-knowledge, it seems that nothing can serves as the distal cause that shared by both the speaker and interpreter. In this thesis I propose that there is a way to specify the distal cause for self-knowledge so that the objectivity of self-knowledge can be explained by the thesis of triangulation. The first chapter concerns how Frege and Russell account for the objectivity of thought. Frege tries to guarantee the objectivity of thought by the objectivity of language, but how the account of the access to thought through language explains the objectivity of thought is unclear, for Frege did not work this out. Russell attempts to explain that propositions are objective because of the corresponding part of the world which made it true or false is objective. However, this attempt presupposed the correspondence theory of truth, a theory that Davidson’s slingshot shot argument shows has no explanatory power, and the verification theory of meaning, which Quine shows is an unsuccessful attempt. In chapter two I will explain how Quine shows that thoughts are objective because observation sentences refers to the way things are. But this approach presupposed the distinction between observation sentences and non-observation sentences in a language, and observation sentences are evidence for knowledge of external world. According to Davidson, however, any theory assuming this distinction fails to block the challenge from scepticism about knowledge of external world. In the first section of chapter three I will present Davidson’s theory of meaning based on empirical theory of truth. In the second part of this chapter I will present Davidson’s argument against scepticism regarding to knowledge. He thinks that beliefs are, by their nature, generally true; thus it is impossible for our beliefs as a whole is false. In chapter four I will show how Davidson explains the objectivity of thought by the thesis of triangulation. And I will argue that there are distal causes for self-knowledge so that the objectivity of self-knowledge can be explained by the thesis of triangulation.