正如哲學上存有諸多反覆的問題，每個哲學者不可避免會遭遇到，而在法學上，同樣的情形亦困擾著法學者。法學上最本原的問題，就是「法是什麼」的問題。對大多數法學者來說，對現行法的認識與應用，是學習法律的主要內容，至於「法是什麼」等較為抽象的思想問題，則因與現實司法的運作脫節，當然也就沒有深究答案的動力和必要。而且此類問題，卻往往難得唯一正解，就算放諸古往今來的法學大家，也未能給出令眾人心悅誠服的回答。 面對納粹的實證法不法，無論是法實證主義者或自然法論者都敗陣下來，本文從實證法不法問題的角度，來說明自然法與實證法思想根本的爭議─有無客觀正確之法。並在認識到自然法與實證法思想的難處之後，再借鑑柏拉圖的法思想，試著以不同於當代的視野，汲取柏拉圖思想的養份，看看能否解開這難解之結。 本文全部共分為五章，除第一章做為導論外，其餘四章做為主題論述，依其結構可分為三部分： 第一部分將簡單敘述自然法與實證法思想的歷史，並提出歷史上實證法不法的問題(特別是納粹德國時期的實踐後果)，說明後來法思想理論對立未決的部分，這些內容將是第二章論述的中心。 第二部分則進入柏拉圖的法思想討論，將先說明柏拉圖所處當時的希臘文化背景，以及其個人經歷，特別是蘇格拉底之死，然後再論述柏拉圖著作中所透露出來有關法律的思想，前面背景的部分會先在第三章予以處理，後面柏拉圖法思想與理論的論述部分則留到第四章討論。 第三部分為綜合論述，也是本文對所提問題的總結回應，將把古典的柏拉圖法思想，與現代的法思想理論結合起來，分析問題象徵的意義，思考能否得出對問題更好的回答，嘗試提出一些看法，此為第五章的內容。 / The perpetual problem of “what is Law” is always asked by the students, the professors, even the philosophers, but no real answer was or is made. The legal positivist like John Austin would declare “laws properly so called are commands of sovereign”, as to another hand, the supporters of theory of natural law would make a completely opposite claim. What shall we do or which side should we believe? In this essay, from the aspect of the contrast between “it ought to be” and “it is”, the history of theory of natural law and legal positivism is tracked down in order to try to figure out the problem of the unlawful laws which the Nazi had made and caused a terrible disaster. Because the result is not so content, so the thought of Plato is reseached as to find out if there would be something that is illuminating. The contents of all chapters of this essay could be digested as follows: In chapter one, as an introduction, it explains the reason that why the essay is written and how it is finished. In chapter two, it tracks down the history of theory of natural law and legal positivism, and shows a horrible instance that caused a catastrophe which neither legal positivism nor theory of natural law could undo. In chapter three, it refers the thought background of Plato including his life and the conditions of contemporary Greek that affected the behaviour and development of Plato. In chapter four, it discusses the thought of Plato such as the theories of form, justice, and legislation with further eyes on his ‘The Ruplic’, ‘Statesman’, and ‘The Laws’. In chapter five, some viewpoints are discussed in advance in order to conclude what is in question. And after that, a temporary conclusion is made.

摘要 本篇論文的討論起點來自柏拉圖如何面對靈魂能夠認知真理的這個可能性。柏拉圖設立那與變動的感覺現象完全分離的「不變動的『相』」作為知識得以成立的條件，這個歷史緣由可從亞里士多德的記載當中知道：一方面，柏拉圖認同克拉梯樓斯與赫拉克利圖學派所主張的感覺現象的永遠流動、無一停留，並因此認為絕不可能有關於感覺現象的知識，然而，另一方面，那致力於倫理事物研究的蘇格拉底則堅持必定有那可被定義的知識對象得以被思考與認知；由於受到這兩方所堅持的信念，柏拉圖則在為了拯救現象並使思考與知識得以可能的情況下，他設立了那必須與變動的感覺現象完全分離的相來作為感覺現象之所以如此存在的原因，並在透過那分有相的感覺現象當中，靈魂得以思考並回憶起關於相的知識，而由此拯救現象並保全靈魂得以思考且獲得知識的可能性。 然而，柏拉圖的分離相論卻有可能引發諸多困難，這主要可由《巴曼尼德斯篇》裡的少年蘇格拉底所遭遇到的三個困境所表現出來：○1少年蘇格拉底對於是否有卑下者的相的存在，顯得猶疑不定；○2由於無法回答相與現象之間到底是如何分有，以致於分有成為不可能；○3更進一步地，正是由於相與現象彼此的完全分離，以致於原本肩負拯救現象這使命的相，到頭來卻反而根本無法拯救現象，而且也面臨無法為人所知的這個最大困境。 這三個困境其實正是柏拉圖真理之路---愛智者如何能擁有那與現象完全分離的相的知識？---所蘊含的兩個一體兩面的論題：第一，思考與知識的可能性如何成立？也就是，相如何拯救現象？第二，愛智者要以什麼樣的方法才能正確地獲得相的知識以成為真正的哲學家？關於第一個論題，筆者認為，柏拉圖在《巴曼尼德斯篇》第二部分的八組推論當中提出一種具有數特徵的存有論，這個存有論綿密、細緻地論說《蒂邁歐篇》裡的宇宙生成論以及「未成書研究」裡的原理論，在這當中，相拯救現象的可能性乃在於---神以其意願與叡智將相形塑於這個數存有的世界並因此使那些在場域裡生滅變化的現象獲得一致性，如此，神的意願（i.e.善）乃作為相得以拯救現象的最具統馭力的原因與原理；關於第二個論題，那能使少年蘇格拉底獲得真理以成為哲學家的訓練，正是那以合理論說所掌握的相為對象的訓練，筆者認為，柏拉圖在這個訓練當中，試圖透過假設法的運用，使得愛智者能緊守在對「是」（i.e.相）的追求上，並得以在一步步的往上探求當中，在最後能以最終的決定性原因---善---來束縛住所有的相，如此，當愛智者能在「善」的指導下以合理論說來正確地指出每個相的真實本質時，這個愛智者也就成為真正的哲學家。 在這樣的解決方式當中，柏拉圖證成了靈魂能夠認知真理的可能性，為自己的真理之路尋得一個合理的立足點。柏拉圖在這當中所奮力搏鬥的，主要並不是亞里士多德在《物理學以後諸篇》A 6.987a33-b10所提及的這些哲學家，而是歷史上的這位伊利亞哲學家---巴曼尼德斯：柏拉圖分離相論的核心來自巴曼尼德斯其毫無生滅變動的「完滿的是」，然而，柏拉圖拯救現象以及保全思考與知識的可能性的這個企圖，卻又是必須對巴曼尼德斯的「完滿的是」提出批判。而在柏拉圖藉由這兩個假設與八組推論來與巴曼尼德斯奮力搏鬥當中，柏拉圖所完成的不僅僅只是解決分離相論所可能引來的困境，而更是走上一條不同於巴曼尼德斯的真理之路，因為現象的拯救是柏拉圖所主要異於巴曼尼德斯的地方，而那使得現象得以被相所拯救的最具統馭力的原因與原理乃在於---宇宙父親的意願與叡智，而這乃作為柏拉圖自己的真理之路的最終磐石。 關鍵詞：相論，分離，分有，善，假設法，柏拉圖，巴曼尼德斯，〈未成書研究〉，《巴曼尼德斯篇》，《蒂邁歐篇》。 / Abstract The aim of this thesis is to show that how Plato might deal with the possibility for soul of knowing the truth. The historical reason for Plato positing the invariable Forms, which are totally apart from the variable sensible things, is remarked by Aristotle that: on the one hand, having been agreed with Cratylus and the Heracllitean doctrines that all sensible things are always in a state of flux and that no science of them exists, yet on the other hand, taking into account the Socrates’ efforts to find general definitions of ethical terms, Plato, having been inspired by both views, thinks that there must be some invariable things, i.e. Forms, which are totally apart from the variable sensible things and could only be thought with logos（or reasonable account）, as the causes of the sensible things. Therefore, the soul could recollect and think of Forms by perceiving these sensible things, which participate in the corresponding Forms. Hence, Plato saves the phenomena and secures the possibility for soul of thinking and knowing the truth by his theory of Forms. However, there might be many problems that arisen from Plato’s theory of Forms. These problems are shown mainly by the three perplexities, which are encountered by the young Socrates in the Parmenides. First, the young Socrates is undecided about whether the base things could have their Forms, second, having been unable to solve the problem of the sharing between the sensible things and Forms, the young Socrates finally has to accept the impossibility of sharing, third, further, just owing to this totally separation that is between the sensible things and Forms, Forms finally could not save the phenomena and could not be known by anyone. Actually, the three perplexities are the two topics of Plato’s way of truth, which is that how the lover of wisdom could know the Forms that are totally separate from the sensible things. The first topic is that, in what way the possibility of thinking and acquiring knowledge could be secured. That is, how the phenomena could be saved by Forms? The second topic is that, in what way the lover of wisdom could acquire the truth and becomes the real philosopher. As for the first, I think that Plato claims a kind of ontology, which has numerical character, in the second part of the Parmenides. This ontology provides deliberately the cosmogony of the Timaeus and the theory of the Principles in the Unwritten Doctrines that could justify the possibility of the phenomena that are saved by Forms. This possibility lies in the god’s nous and will, i.e. the world that has numerical character is fashioned by the god with Forms as model, and then the becoming phenomena that cling to the receptacle are saved and intelligible. Therefore, the god’s will is the supremely valid cause and principle of this possibility. As for the second, this exercise that can make the young Socrates as a real philosopher if he takes it into practice is the training, which takes Forms as its objects and be practiced in hypothetical method. I think the reason for Plato of using the hypothetical method is that this hypothetical method can make the lover of wisdom to cling to Forms when he is putting this exercise into practice, and in this upward process systematically, finally, he can fasten all the Forms with the final cause, i.e. the good. Therefore, when the lover of wisdom could show the real essence of each Form with reasonable account under the guidance of the good, he at that time is a real philosopher. Under this solution, Plato justifies the possibility for soul of knowing the truth, and makes his way of truth possible. In this fighting, those with whom Plato fights are not those philosophers that are remarked by Aristotle in Metaphysics A 6.987a33-b10, but the philosopher of Elea, Parmenides. On the one hand, the key point of Plato’s theory of Forms is coming from Parmenides’ concept of Being, which is ungenerated and imperishable, yet on the other hand, the attempt for the possibility of saving the phenomena and for soul to know the truth is urging Plato to put Parmenides’ claim to the question. Then what Plato has done in this fighting, which mainly occurs in the second part of the Parmenides, is that as he is solving these perplexities, he at the same time is stepping upon another way of truth, which is different from Parmenides. In this fighting, saving phenomena is the main difference between Plato and Parmenides. The god’s nous and will is the supremely valid cause and principle of the saved phenomena and this most supreme cause is the coping-stone for Plato’s way of truth. Keywords: Plato’s theory of Forms, separate, participate, the good, the hypothetical method, Plato, Parmenides, the Unwritten Doctrines, the Parmenides, the Timaeus.