線喻希臘語γραμμὴ δίχα τετμημένη )由希臘哲學家柏拉圖描寫蘇格拉底和格老孔之間的對話時(509d–511e)提出,當蘇格拉底描述完日喻時,格老孔要求蘇格拉底進一步解釋「日喻」時提出了線喻 。蘇格拉底要求格老孔(Glaucon)設想一條不等分的線,然後把這條線分成兩部分。蘇格拉底解釋說,由此產生了四個部分,這四部份分別代表了四個「層次」(παθήματα)。較低的兩個部分為感官,而較高的兩個部分為可理解性。這些分別闡述了從猜想( εἰκασία )到信念( πίστις )、從思想( διάνοια )到最終理解( νόησις )。這顯示了從現實一直提升到最高真理。此外,這種類比不僅闡述了形上學的理論,而且牽涉到心理學知識論的觀點。

描述

 
線喻( A至C )代表可見世界,( CE )代表可理解的世界。 [1]

《理想國》 (509d–510a)中,柏拉圖用這種方式描述了線喻:

Now take a line which has been cut into two unequal parts, and divide each of them again in the same proportion,[2] and suppose the two main divisions to answer, one to the visible and the other to the intelligible, and then compare the subdivisions in respect of their clearness and want of clearness, and you will find that the first section in the sphere of the visible consists of images. And by images I mean, in the first place, shadows, and in the second place, reflections in water and in solid, smooth and polished bodies and the like: Do you understand?

Yes, I understand.

Imagine, now, the other section, of which this is only the resemblance, to include the animals which we see, and everything that grows or is made.[3]

(翻譯:那麼請你畫一條線來表示它們,把這條線分成不等的兩部分,然後把它們按照同樣的比例再分別分成兩部分。假定原來的兩個部分中的一個部分相當於可見世界,另一部分相當於可知世界,然後我們再根據其清晰程度來比較第二次分成的部分,這樣你就會看到可見世界的一部分表示影像。所謂影像我指的首先是陰影,其次是在水裡或表面光滑的物體上反射出來的影子或其他類似的的東西。你懂我的意思嗎?

我懂。

至於第二部分表示的是實際的東西,即我們周圍的動物和植物,以及一切自然物和人造物。)

可見的世界

因此, AB代表物理事物的影子和反射,而BC代表物理事物本身。這個對應於兩種知識:猜想信念(πίστιςpistis)。這一層代表著我們的日常經驗(εἰκασία eikasia)。當中猜想屬於事物的影像,而信念則為事物的本身。 [4]蒂邁歐篇(Timaeus)中,「猜想」還包括了「普遍思想的觀點」,而自然科學則在信念類別當中。

可理解的世界

根據一些翻譯,可理解世界的CE段被劃分為與AC相同的百份比,從而給出了CD和DE細分(可以得出CD的長度必須與BC相同): [5]

There are two subdivisions, in the lower of which the soul uses the figures given by the former division as images; the enquiry can only be hypothetical, and instead of going upwards to a principle descends to the other end; in the higher of the two, the soul passes out of hypotheses, and goes up to a principle which is above hypotheses, making no use of images as in the former case, but proceeding only in and through the ideas themselves (510b).[3]

(翻譯:把這個世界分成兩部分,在一個部分中,人的靈魂被迫把可見世界中那些本身也有自己的影子的實際事物作為影像,從假設出發進行考察,但不是從假設上升到原則,而是從假設下降到結論;而另一個部分中,人的靈魂則朝著另一方面前進,從假設上升到非假設的原則,並且不用在前一部分中所使用的影像,而只用「類型」,完全依據「類型」來取得系統的進展。)

柏拉圖把CD描述為數學世界(διάνοια dianoia ),[4]當中更包含了數學哲學,如對幾何線條進行了討論。:

And when I speak of the other division of the intelligible, you will understand me to speak of that other sort of knowledge which reason herself attains by the power of dialectic, using the hypotheses not as first principles, but only as hypotheses – that is to say, as steps and points of departure into a world which is above hypotheses, in order that she may soar beyond them to the first principle of the whole (511b).[3]

(翻譯:至於可知世界的另一部分,你要明白,我指的是理性本身憑著辯證法的力量可以把握的東西。在這裡,假設不是被當作絕對的起點,而是僅僅被用作假設,也就是說假設是基礎、立足點和跳板,以便能從這個暫時的起點上升到一個不是假設的地方,在這個地方才是一切的起點,上升到這裡並且從中獲得第一原理。)

柏拉圖在這裡使用普通對象與它們的陰影或反射之間的熟悉關係來說明整個物理世界與整個思想世界(形式)之間的關係。前者由對後者的一系列經過的反射組成,後者是永恆的,更加真實的和「真實的」。此外,我們對思想的了解(實際上的確確實如此)要比對純物理世界的了解更高。特別是,對形式的了解會導致對善的觀念(形式)的了解。 [1]

分割 知識或意見的類型  心理思考 對象類型 心靈或眼睛的思考 相對真理與現實
DE 理性 ( νόησις 知識(理解):不限於可理解( νοητόν )的都能夠理解 這些觀念都是由善形式所賦予的真理(τὸαὐτὸἀγαθθν) 對於心靈的一切假設已不需使用辯證法驗證,完全使用理型,總是思考最初原理。 最高
CD 思想(διάνοια) 知識(思想):認為知識不限於可理解的思想 對於幾何和數的想法 從心靈上的假設,總是思考最終的結論
BC 信念(πίστις 觀點(信念):關於可見事物的本身 可見事物的本身(ὁρατά 眼睛觀察可見物體的本身
AB 猜想(εikaκασία) 觀點(想像力):關於一切的猜想 可見事物的猜想(εἰκόνες 眼睛對觀察可見事物之猜測 最低

形上學的重要性

線喻是柏拉圖形上學的基石。這種架構顯示了柏拉圖的形上學知識論倫理學的全貌。哲學家僅了解思想(形式)是不夠的,他還必須理解思想與架構的所有四個層次的關係,才能完全了解其內容。[6][7][8]在《理想國》內,哲學家必須理解正義,以過上公正的生活、並能組織和治理公正的國家。[9]

線喻也可作為我們過去和將來大多數形上學的指南。最低的層次柏拉圖描述為「有生有滅的世界」(理想國,508d),這成為了赫拉克利特對於流變的哲學基礎。第二層為一個固定的物理世界, [10] [11]這也成為了亞里斯多德的形上學的基礎。第三級則是畢達哥拉斯的數學哲學。第四層就是柏拉圖的理型和巴門尼德所認為的現實世界,即最高層思想的世界。

知識論意義

柏拉圖擁有非常嚴格的知識概念。例如,他不接受專業知識,也不接受直接的感知(請參見泰阿泰德篇 ),也不接受對物理世界(即美諾篇)的信仰作為知識基礎。哲學家僅了解思想(形式)是不夠的,他還必須理解思想與結構的所有四個層次之間的關係,才能完全了解一切內容。 [12]因此,在大多數早期的蘇格拉底對話中,蘇格拉底否認自己和他人的知識。

對於第一個層次:「有生有滅的世界」。柏拉圖否定了這世界能夠擁有知識。 [13]他認為時間的變化使得知識不斷變更。因此,必須在不同的時間引入不同的思想。柏拉圖認為,如果要得到知識,其他三個層次必須固定。而第三和第四層次的數學和思想已經永恆不變。但是,在第一和第二層次的世界亦需要保持不變﹏故此,柏拉圖在《理想國》第四章中[14]闡述了根據經驗所得出的[15] [16] [17]公理限制、禁止運動和移動觀點。[10] [18]

參看

參考文獻

  1. ^ 1.0 1.1 "divided line," The Cambridge Dictionary of Philosophy, 2nd edition, Cambridge University Press, 1999, ISBN 0-521-63722-8, p. 239.
  2. ^ Older Greek texts do not differentiate unequal from an equal (ανίσα, αν ίσα)
  3. ^ 3.0 3.1 3.2 Plato, The Republic, Book 6, translated by Benjamin Jowett, online 網際網路檔案館存檔,存檔日期18 April 2009.
  4. ^ 4.0 4.1 Desmond Lee and Rachana Kamtekar, The Republic, Notes to Book 6, Penguin, 1987, ISBN 0-14-044914-0.
  5. ^ Let the length of AE be equal to   and that of AC equal to  , where   (following Socrates, however,  ; insofar as the equality of the lengths of BC and CD is concerned, the latter restriction is of no significance). The length of CE is thus equal to  . It follows that the length of BC must be equal to  , which is seen to be equal to the length of CD.
  6. ^ Gail Fine, Knowledge and Belief in Republic V-VII, in G. Fine (ed.) Plato I (1990), also in S. Everson (ed.) Cambridge Companions to Ancient Thought I: Epistemology (Cambridge University Press: New York, 1990), pp. 85–115.
  7. ^ Nicholas Denyer, Sun and line: the role of the Good, in G. R. F. Ferrari (ed.) The Cambridge Companion to Plato's Republic (Cambridge University Press: New York, 2007), pp. 284–309.
  8. ^ Republic 520c頁面存檔備份,存於網際網路檔案館): "For once habituated ... you will know what each of the 'idols' is and whereof it is a semblance, because you have seen the reality of the beautiful, the just and the good."
  9. ^ Rachel G.K. Singpurwalla, Plato’s Defense of Justice in the Republic頁面存檔備份,存於網際網路檔案館) "justice is a virtue appropriate to both cities and individuals, and the nature or form of justice is the same in both (Republic, 435a)."
  10. ^ 10.0 10.1 James Danaher, The Laws of Thought頁面存檔備份,存於網際網路檔案館) "The restrictions Plato places on the laws of thought (i.e., "in the same respect," and "at the same time,") are an attempt to isolate the object of thought by removing it from all other time but the present and all respects but one." 引用錯誤:帶有name屬性「Danaher」的<ref>標籤用不同內容定義了多次
  11. ^ Cratylus 439d-e頁面存檔備份,存於網際網路檔案館) "For if it is ever in the same state, then obviously at that time it is not changing (Plato's realism); and if it is always in the same state and is always the same, how can it ever change or move without relinquishing its own form (Aristotle's realism)"
  12. ^ Republic 520c頁面存檔備份,存於網際網路檔案館) "For once habituated you will discern them infinitely better than the dwellers there, and you will know what each of the 'idols' is and whereof it is a semblance, because you have seen the reality of the beautiful, the just and the good."
  13. ^ Cratylus 439d-e頁面存檔備份,存於網際網路檔案館) "How, then, can that which is never in the same state be anything? ... nor can it be known by anyone."
  14. ^ Republic 4.436b頁面存檔備份,存於網際網路檔案館) "It is obvious that the same thing will never do or suffer opposites in the same respect in relation to the same thing and at the same time"
  15. ^ Republic 4.437a頁面存檔備份,存於網際網路檔案館) "let us proceed on the hypothesis that this is so, with the understanding that, if it ever appear otherwise, everything that results from the assumption shall be invalidated"
  16. ^ Also see the Timaeus 29c頁面存檔備份,存於網際網路檔案館) on empirical "likelihood"
  17. ^ It is interesting to note that modern logical analysis claims to prove that the potentially falsifiable "empirical content of a theory is exactly captured by ... axiomatization ... that uses axioms which are universal negations of conjunctions of atomic formulas" (C. Chambers, The Axiomatic Structure of Empirical Content) 網際網路檔案館存檔,存檔日期27 June 2010.
  18. ^ Plato's Principle of Non-Contradiction (Republic, 4.436b) for the objective, physical world is presented with three axiomatic restrictions: The same thing ... cannot act or be acted upon ... in contrary ways ... (1) in the same part (2) in relation to the same thing (3) at the same time.