线喻希腊语γραμμὴ δίχα τετμημένη )由希腊哲学家柏拉图描写苏格拉底和格老孔之间的对话时(509d–511e)提出,当苏格拉底描述完日喻时,格老孔要求苏格拉底进一步解释“日喻”时提出了线喻 。苏格拉底要求格老孔(Glaucon)设想一条不等分的线,然后把这条线分成两部分。苏格拉底解释说,由此产生了四个部分,这四部分分别代表了四个“层次”(παθήματα)。较低的两个部分为感官,而较高的两个部分为可理解性。这些分别阐述了从猜想( εἰκασία )到信念( πίστις )、从思想( διάνοια )到最终理解( νόησις )。这显示了从现实一直提升到最高真理。此外,这种类比不仅阐述了形而上学的理论,而且牵涉到心理学知识论的观点。

描述

 
线喻( A至C )代表可见世界,( CE )代表可理解的世界。 [1]

《理想国》 (509d–510a)中,柏拉图用这种方式描述了线喻:

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]

(翻译:那么请你画一条线来表示它们,把这条线分成不等的两部分,然后把它们按照同样的比例再分别分成两部分。假定原来的两个部分中的一个部分相当于可见世界,另一部分相当于可知世界,然后我们再根据其清晰程度来比较第二次分成的部分,这样你就会看到可见世界的一部分表示影像。所谓影像我指的首先是阴影,其次是在水里或表面光滑的物体上反射出来的影子或其他类似的的东西。你懂我的意思吗?

我懂。

至于第二部分表示的是实际的东西,即我们周围的动物和植物,以及一切自然物和人造物。)

可见的世界

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。这个对应于两种知识:猜想信念(πίστιςpistis)。这一层代表着我们的日常经验(εἰκασία eikasia)。当中猜想属于事物的影像,而信念则为事物的本身。 [4]蒂迈欧篇(Timaeus)中,“猜想”还包括了“普遍思想的观点”,而自然科学则在信念类别当中。

可理解的世界

根据一些翻译,可理解世界的CE段被划分为与AC相同的百份比,从而给出了CD和DE细分(可以得出CD的长度必须与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]

(翻译:把这个世界分成两部分,在一个部分中,人的灵魂被迫把可见世界中那些本身也有自己的影子的实际事物作为影像,从假设出发进行考察,但不是从假设上升到原则,而是从假设下降到结论;而另一个部分中,人的灵魂则朝着另一方面前进,从假设上升到非假设的原则,并且不用在前一部分中所使用的影像,而只用“类型”,完全依据“类型”来取得系统的进展。)

柏拉图把CD描述为数学世界(διάνοια dianoia ),[4]当中更包含了数学哲学,如对几何线条进行了讨论。:

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]

(翻译:至于可知世界的另一部分,你要明白,我指的是理性本身凭着辩证法的力量可以把握的东西。在这里,假设不是被当作绝对的起点,而是仅仅被用作假设,也就是说假设是基础、立足点和跳板,以便能从这个暂时的起点上升到一个不是假设的地方,在这个地方才是一切的起点,上升到这里并且从中获得第一原理。)

柏拉图在这里使用普通对象与它们的阴影或反射之间的熟悉关系来说明整个物理世界与整个思想世界(形式)之间的关系。前者由对后者的一系列经过的反射组成,后者是永恒的,更加真实的和“真实的”。此外,我们对思想的了解(实际上的确确实如此)要比对纯物理世界的了解更高。特别是,对形式的了解会导致对善的观念(形式)的了解。 [1]

分割 知识或意见的类型  心理思考 对象类型 心灵或眼睛的思考 相对真理与现实
DE 理性 ( νόησις 知识(理解):不限于可理解( νοητόν )的都能够理解 这些观念都是由善形式所赋予的真理(τὸαὐτὸἀγαθθν) 对于心灵的一切假设已不需使用辩证法验证,完全使用理型,总是思考最初原理。 最高
CD 思想(διάνοια) 知识(思想):认为知识不限于可理解的思想 对于几何和数的想法 从心灵上的假设,总是思考最终的结论
BC 信念(πίστις 观点(信念):关于可见事物的本身 可见事物的本身(ὁρατά 眼睛观察可见物体的本身
AB 猜想(εikaκασία) 观点(想象力):关于一切的猜想 可见事物的猜想(εἰκόνες 眼睛对观察可见事物之猜测 最低

形而上学的重要性

线喻是柏拉图形而上学的基石。这种架构显示了柏拉图的形而上学知识论伦理学的全貌。哲学家仅了解思想(形式)是不够的,他还必须理解思想与架构的所有四个层次的关系,才能完全了解其内容。[6][7][8]在《理想国》内,哲学家必须理解正义,以过上公正的生活、并能组织和治理公正的国家。[9]

线喻也可作为我们过去和将来大多数形而上学的指南。最低的层次柏拉图描述为“有生有灭的世界”(理想国,508d),这成为了赫拉克利特对于流变的哲学基础。第二层为一个固定的物理世界, [10] [11]这也成为了亚里士多德的形而上学的基础。第三级则是毕达哥拉斯的数学哲学。第四层就是柏拉图的理型和巴门尼德所认为的现实世界,即最高层思想的世界。

知识论意义

柏拉图拥有非常严格的知识概念。例如,他不接受专业知识,也不接受直接的感知(请参见泰阿泰德篇 ),也不接受对物理世界(即美诺篇)的信仰作为知识基础。哲学家仅了解思想(形式)是不够的,他还必须理解思想与结构的所有四个层次之间的关系,才能完全了解一切内容。 [12]因此,在大多数早期的苏格拉底对话中,苏格拉底否认自己和他人的知识。

对于第一个层次:“有生有灭的世界”。柏拉图否定了这世界能够拥有知识。 [13]他认为时间的变化使得知识不断变更。因此,必须在不同的时间引入不同的思想。柏拉图认为,如果要得到知识,其他三个层次必须固定。而第三和第四层次的数学和思想已经永恒不变。但是,在第一和第二层次的世界亦需要保持不变﹏故此,柏拉图在《理想国》第四章中[14]阐述了根据经验所得出的[15] [16] [17]公理限制、禁止运动和移动观点。[10] [18]

参看

参考文献

  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 互联网档案馆存档,存档日期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页面存档备份,存于互联网档案馆): "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页面存档备份,存于互联网档案馆) "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页面存档备份,存于互联网档案馆) "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." 引用错误:带有name属性“Danaher”的<ref>标签用不同内容定义了多次
  11. ^ Cratylus 439d-e页面存档备份,存于互联网档案馆) "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页面存档备份,存于互联网档案馆) "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页面存档备份,存于互联网档案馆) "How, then, can that which is never in the same state be anything? ... nor can it be known by anyone."
  14. ^ Republic 4.436b页面存档备份,存于互联网档案馆) "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页面存档备份,存于互联网档案馆) "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页面存档备份,存于互联网档案馆) 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) 互联网档案馆存档,存档日期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.