談談正確運用自己的理性
在各門學問裡尋求真理的方法
作者 / 笛卡爾
翻譯 / 王太慶
I would gladly go on and reveal the whole chain of the other truths that I deduced from these first ones. But in order to achieve this end, it would be necessary here for me to broach several questions that are controversial among l earned men with whom I do not wish to fall out, and so I believe it would be best for me to abstain from doing this, and state only in broad terms what these questions are, in order to leave wiser heads to judge whether it would be profitable for the public to be informed about them in greater detail. I have always stuck to the decision I took not to posit any principle other than that which I have just used to prove the existence of God and of the soul, and not to take anything to be true which did not seem to me clearer and more certain than the proofs of geometers had previously seemed. And yet I venture to say that I have not only found the way to satisfy myself in a short space of time about all the principal difficulties usually discussed in philosophy, but I have also come to see certain laws which God has established in such a way in nature, and of which He has imprinted notions of such a kind in our souls, that after sufficient reflection on them, we cannot doubt that they are strictly observed in everything that exists or occurs in the world. Moreover, by considering what follows from these laws, it seems to me that I have discovered many truths more useful and important than anything I had hitherto learned or even hoped to learn.
我從上面那些基本原理推出了整整一系列其他的真理，很樂意在這裡從頭到尾說給大家聽聽。可是要這樣做現在就需要談許多問題，那些問題學者們還在爭論，我又不想跟他們糾纏，所以我想最好還是不那麼做，只是大致說一說那些真理是怎麼一回事，讓高明的人看看有沒有必要給大家細講。我一直堅持自己已經下定的那個決心，除了剛才用來證明神和靈魂存在的那一條原理以外決不設定任何原理，任何一種看法，只要我覺得它清楚可靠的程度比不上幾何學家已往的證明，就決不把它當作真的接受；可是我敢大膽地說，我不僅找到竅門在很短的時間內滿意地弄清了哲學上經常討論的一切主要難題，而且摸出了若干規律，它們是由神牢牢地樹立在自然界的，神又把它們的概念深深地印在我們的靈魂裡面。所以我們經過充分反省之後就會毫不猶疑地相信，世界上的萬事萬物無不嚴格遵守這些規律。我再進一步觀察，看到這些規律是聯成一氣的，因此我認為自己已經發現了許多非常有用、非常重要的真理，勝過我從前學過的一切，甚至超過我從前希望學到的一切。
But since I tried to explain the most important of these in a treatise which certain considerations prevent me from publishing,* I cannot let them be known better than by saying here briefly what the treatise contains. Before I started writing it, I had intended to include in it everything that I believed I knew about the nature of material things. But just like those painters who, being unable to represent equally in a flat picture all the various faces of a solid body, choose only one of the principal ones which they place in the light, leaving the others in shadow, representing them to the extent that one can see them when one looks at the chosen face; so also, fearing that I could not put everything that I had in my mind in my discourse, I undertook only to reveal fully my conception of light; there after, I took the opportunity of adding something about the sun and the fixed stars, because light proceeds almost wholly from them; something about the heavens, because they transmit it; something about the planets, the comets, and the earth, because they reflect it; and in particular something about terrestrial bodies, because they are either coloured, or transparent, or luminous; and finally something about man, because he is the spectator of all this. And in order to remove these things from the spot light and to be able to say more freely what I thought about them without being obliged either to confirm or refute the opinions of learned men, I decided to leave this earth wholly for them to discuss, and to speak only of what would happen in a new world, if God were now to create enough matter to compose it somewhere in imaginary space,* and if He were to agitate the different parts of this matter in diverse and indiscriminate ways so as to create from it a chaos as confused as any poet could possibly imagine; and that He then did no more than sustain nature in His usual manner, leaving it to act according to the laws He has established. So I first described this matter and tried to represent it so that there is nothing in the world, I think, clearer and more intelligible, except what has just been said of God and the soul; for I even made the explicit supposition expressly that it contained none of the forms or qualities* which are discussed by scholastic philosophers, and that it had nothing in general that was not so naturally known to our souls that we could not even pretend to be ignorant of it. Further, I revealed what were the laws of nature; and basing my reasoning on no other principle than the infinite perfections of God, I set out to prove all those laws about which one might have had some doubt, and to show that they are such that even if God had created many worlds, there could be not be any in which they could have failed to be observed. After that, I demonstrated how the greater part of the matter of this chaos must, in consequence of these laws, be disposed and arranged in away which made it similar to the heavens above us; how, at the same time, some of its parts had to compose an earth, some others planets and comets, yet others a sun and fixed stars. And here, enlarging on the subject of light,* I explained in detail the nature of the light to be found in the sun and the heavenly bodies, the way it crossed in an instant the immense expanses of the heavens, and how it was reflected from the planets and the comets towards the earth. I added also many things about the substance, position, motions, and all the various qualities of these heavens and stars; so that I thought I had said enough to show that nothing was to be observed in those of our world which must not or at least could not appear wholly similar to the world I was describing. Next, I came to speak about the earth in particular, and to discuss how, although I had made the explicit supposition that God conferred no weight* on the matter of which it was composed, all its parts nonetheless tended exactly towards its centre; how, there being water and air on its surface, the dispositions of the heavens and the heavenly bodies (principally the moon) must cause tidal movement similar in every circumstance to that which we observe in our seas; and together with all this, a certain current, as much of the water as of the air, from east to west, such as we find here in our tropics; how mountains, seas, springs, and rivers could naturally form themselves, metals appear in the mines, plants grow in the countryside, and in general, how all the bodies that are called mixed or composed come into being there. And among other things, because apart from the heavenly bodies I knew of nothing in the world which produces light apart from fire, I set out to explain very clearly everything which pertains to its nature, how it comes about and how it sustains itself; how there is sometimes only heat without light and sometimes only light without heat; how it can introduce different colours and various other qualities into different bodies; how it melts some things and hardens others, how it can consume nearly all of them or turn them into ashes and smoke; and finally, how it can form glass from these ashes, by nothing other than the power of its action. I took particular pleasure in describing this, for the transmutation of ashes into glass seemed to me as remarkable a transformation as any that occurs in nature.
我寫過一部論著，試圖說明這些真理的主要部分，由於某種顧慮，沒有把它發表；大家不知道那部書講的是什麼內容，所以我只好在這裡給它作一個內容提要。那部書的論述對象是各種物質性的東西的本性。我在動手寫它之前，曾經打算把這一方面我認為知道的東西統統寫進去。然而，畫家是不能在一個平面上把立體的各方面同等地表現出來的，只有從其中選擇一個主要方面正對著光線，把其他的方面都放在背陰處，使人們看正面的時候可以附帶看到側面。同樣情形，我的論述裡也無法包羅我的全部思想，所以我只用較大的篇幅表達我對光的理解，然後附帶講一講太陽和恆星，因為光幾乎全部是從那裡發出來的；再講一講天宇，因為它是傳導光的；再講一講行星、彗星和地球，因為它們是反射光的；再專門講一講地球上的各種物體，因為它們有的是有色的，有的是透明的，有的是發光的；最後講一講人，因為他是這些東西的觀察者。為了把這一切往背陰的那邊挪挪，以便比較自由地說出我自己的判斷，而不必對學者們所接受的看法表示贊成或反對，我甚至於決定拋開我們這個世界，也就是說，假定現在神在想像的空間裡某個地方創造出一團物質，足夠構成這個世界，再把這團物質的各部分亂七八糟地攪和在一起，混淆得跟詩人所能設想的一樣，然後不再做別的事情，只是向自然界提供通常的協助，讓它遵照他所建立的規律活動，看看會發生什麼事情。於是我就首先描述這個物質，力求說明：除了剛才說過的神和靈魂的本性以外，世界上的任何東西，在我看來都沒有物質的本性那樣清楚，那樣容易了解。因為我甚至明確地設定：物質裡並沒有經院學者們所爭論那些「形式」或「性質」，其中的一切都是我們的靈魂本來就認識的，誰也不能假裝不知道。然後我就說明有哪些自然規律，我並不依靠任何別的原理，只是根據神的無限完滿進行推理，力求對那些可以置疑的規律作出證明，說明它們的確是自然規律，即便神創造了許多世界，也沒有一個世界不遵守它們。接著我又證明，這團混沌中的絕大部分物質必定按照這些規律以一定的方式自行安排調整，形成與我們的天宇相似的東西，它的某些部分則構成一個地球、若干行星和彗星，另一些部分則構成一個太陽、若干恆星。在這個地方我進而討論光這個主題，用很大的篇幅說明光是什麼，以及它如何必定在太陽和恆星裡出現，又從那裡出發在一瞬間穿過天宇中的廣大空間，並且從行星和彗星上向地球反射。我又作了許多補充，說明那些天宇和星球的質地、位置、運動和各種性質，我想說了這些就足可以表明我們這個世界上的天宇和星球也應當跟我所描述的那個世界上的一模一樣，至少可以一樣。往下我就特別講一講地球，具體地說明：雖然我已經明確設定神並沒有把重量放進構成地球的物質，地球上的各部分仍然絲毫不差地引向地心；地面上既然有水和空氣，那麼，天宇和星辰的構造，主要是月球的構造，就不能不在那裡引起潮汐，在各方面都跟我們在海裡見到的一樣，此外還引起一種洋流和氣流，從東到西，跟我們在熱帶地方見到的一樣；何以山脈、海洋、泉水、河流能在地球上自然形成，礦物能在那裡的礦山上產生，植物能在那裡的原野上長出，各式各樣的所謂混合物或組合物能在那裡造成。由於我發現除了星球之外世界上只有火產生光，所以我撇開其他現象專門下工夫詳細說明那些與火有關的事情，指出火是怎麼產生的，怎麼維持的，何以有時候有熱無光，有時候有光無熱；它何以能夠在不同的物體上引出不同的顏色以及不同的其他性質；它何以把某些東西燒化，把另一些東西燒硬；它何以能燒掉幾乎所有的東西，把它們燒成灰和煙；以及它如何能單憑猛燒把那些灰燼燒成玻璃。這種從灰燼到玻璃的轉化我覺得跟自然界發生的其他各種轉化一樣奇妙，所以我特別樂意描述它。
Yet I did not wish to infer from all this that our world was created in the way I suggested; for it is much more plausible that from the beginning God made it as it was to be. But it is certain (and this is an opinion widely held among theologians) that the act by which He conserves the world is the same as that by which He created it.* So, even if He might not have given it any other form at the beginning than chaos, provided that He established the laws of nature and gave nature the help to act as it usually acts, we may believe, without casting doubt upon the miracle of creation,* that all purely material things would have been able, in time, to make themselves into what we see them to be at present in this way alone. And their nature is much easier to conceive of, when we think of their gradual emergence in this way, than when we only consider them in their final form.
儘管這樣，我還不想就此得出結論說：這個世界就是照我說的那種方式創造出來的，因為也很可能神當初一下就把它弄成了定型。可是確確實實，神學家們也一致公認，神現在保持世界的行動就是他當初創造世界的那個行動。既然如此，即便神當初給予世界的形式只是混沌一團，只要神建立了自然規律，向世界提供協助，使它照常活動，我們還是滿可以相信：單憑這一點，各種純粹物質性的東西是能夠逐漸變成我們現在看到的這個樣子的，這跟創世奇蹟並不衝突；而且，把它們看成以這種方式逐漸形成，要比看成一次定型更容易掌握它們的本性。
From the description of inanimate bodies and plants I passed to that of animals, and in particular to that of men. But because I did not yet know enough to speak about it in the same way as I did about the rest, that is to say, by proving effects from causes,and showing from what elements and by what process nature must produce them, I contented myself with the supposition that God formed the body of a man,exactly like our own both in the external shape of his members and in the internal configuration of his organs, constituting him of no other matter than that which I had already described, and without placing in him in the beginning a rational soul, or anything else which could function as a vegetative or sensitive soul,* but merely kindling in his heart one of those fires without light which I had already explained and whose nature I conceived of as no different from the fire that heats hay when it has been stored before it was dry, or makes new wine rise in temperature, when it is left to ferment on the lees. For, in investigating the functions that could as a consequence be in this body, I found precisely all those which can be in us without our thinking of them, and to which our soul, that is to say, that part of us distinct from the body whose sole nature, as has been said above, is to think, contributes nothing; these functions are the same as those in which irrational animals may be said to resemble us. But I was unable to find in this body any of those functions which, being dependent on thought, are the only ones that belong to us as human beings, whereas I found them all there subsequently, once I had supposed that God created a rational soul and that He joined it to this body in a particular way which I described.
描述了無生命的物體和植物之後，我就進而描述動物，特別是人。可是我這方面的知識不夠，不能用上面那種格式來講，也就是說，不能用原因來證明結果，說不出自然界是用什麼種子、以什麼方式產生出這類東西的。所以我姑且假定神造了一個人的身體，不論在肢體的外形上，還是在器官的內部構造上，都跟我們每個人的完全一樣，採用的材料就是我所描述的那種物質，一開頭並沒有放進一個理性靈魂，也沒有放進什麼別的東西代替生長靈魂或感覺靈魂，只不過在他的心臟裡點了一把上面說過的那種無光之火；這種火的本性，我想同那些使溼草堆發熱、使葡萄釀成新酒的火是一樣的。因為點著那把火之後那個身體裡就可以產生各種機能。我仔細檢查，發現只要我們不思想，因而不觸動靈魂這個與形體分立的部分（上面已經說過，靈魂的本性只是思想），我們身上所能產生的也就恰恰是那些機能，這一方面可以說無理性的動物跟我們是一樣的，可是我卻不能因此在那個身體裡找到什麼依靠思想的、純粹屬於我們的機能；後來我假定神創造了一個理性靈魂，用我描述的那種特定的方式把它結合到那個身體上，我就在其中發現這類機能了。
But so that one may see how I dealt with this matter, I wish to give here the explanation of the movement of the heart and the arteries, from which, being the first and most general movement that is observed in animals, readers will determine more easily what they must think about all the others. And so that they might have less difficulty understanding what I shall say about it, I should like those who are unversed in an atomy to take the trouble, before reading this, of having the heart of a large animal with lungs dissected before their eyes (for it is in all respects sufficiently like that of a man) and of having its two chambers or cavities pointed out to them. First, the one which is on the right side, to which two very wide tubes are connected; that is, the vena cava, which is the principal receptacle of blood and, as it were, the trunk of the tree of which all other veins in the body are the branches; and the vena arteriosa, which has been ill-named, being in fact an artery, which has its origin in the heart, and having emerged from it, divides into many branches that spread throughout the lungs. Next, the cavity on the left side, to which two tubes are connected in the same way, which areas wide or wider than the preceding ones; that is, the arteria venosa, which has also been ill-named, because it is nothing other than a vein, which comes from the lungs where it is divided into many branches, inter twined with those of the vena arteriosa, and those with the tube called the trachea through which the air we breathe enters; and the aorta which, coming out from the heart, sends its branches throughout the body. I should also like my readers to be shown carefully the eleven small membranes which, like so many little doors, open and close the four apertures which are in these two cavities; namely, three at the entrance to the vena cava, where they are so disposed that they cannot prevent the blood it contains from flowing into the right cavity of the heart and yet at the same time completely stop the blood from leaving it; three at the entrance to the vena arteriosa, which, being disposed in the opposite way, allow the blood in that cavity to pass into the lungs, but stop the blood in the lungs from returning to the heart; and two others at the entrance to the arteria venosa, which allow in the same way the blood from the lungs to flow towards the left cavity of the heart, but prevent it from returning; and three at the entrance to the aorta, which allow blood to leave the heart but stop it returning. And there is no need to look for any other cause for the number of these membranes other than that the aperture of the arteria venosa, being oval in shape on account of its location, can easily be closed with two of them, whereas the others, being round, can more easily be closed with three. Moreover, I would wish my readers to have pointed out to them that the aorta and the vena arteriosa are of a much harder and firmer texture than the arteria venosa and the vena cava, and that these latter two widen out before entering the heart to form two pouches, as it were, called the auricles of the heart, which are composed of similar substance to the heart itself. They will observe also that there is always more heat in the heart than in any other part of the body; and finally, that this heat is able to cause a drop of blood entering its cavities to swell up at once and to dilate, in the same way that all liquids do when they are allowed to fall drop by drop into a very hot vessel.
為了使大家明白我在那部書裡是怎樣討論這個問題的，我要在這裡說明一下心臟和動脈的運動，因為這是動物身上可以觀察到的最基本、最一般的運動，知道了它就很容易知道對其他各種運動應當怎樣看。為了使大家比較容易了解我的說明，我要請不熟悉解剖的人費點力氣，在讀我的說明之前先切開一個有肺大動物的心臟放在面前（因為它的各部分都很像人的心臟），看看其中的兩個心舍或心腔：先看右邊的一個，有兩根粗管子連在上面，一根是腔靜脈，這是主要的貯血器，好像樹幹，體內其他靜脈都是它的分支；另一根是動靜脈，這個名字取得不好，因為他實際上是一根動脈，以心臟為出發點，然後形成許多分支，布滿兩肺。再看左邊一個心腔，也同樣有兩根管子連著，跟上面說的兩根同樣粗，或者更粗，一根是靜動脈，這個名字也取得不好，因為它只是一根靜脈，來自兩肺，在肺裡有許多分支，跟動靜脈的分支交織在一起，又跟氣管的分支交織在一起，空氣是通過氣管吸進來的；另外一根管子是大動脈，從心臟通出去，把分支通到全身各處。我還要請大家看一看十一片小皮膜，好像十一座小門，管著這兩個心腔上四個口子的啟閉：三片在腔靜脈的人口，裝配得完全不妨礙其中的血液流人右腔，卻正好使血液不能從心臟往外流；三片在動靜脈的人口，裝配得正好相反，只容許右腔裡的血液流到肺裡，不容許肺裡的血液往回流；另外兩片在靜動脈的人口，許可血液從肺裡往左腔流，不許它往回倒；還有三片在大動脈的人口，容許血液從心臟流出，不許它往心臟回流。這些皮膜的數目也很自然，用不著再找什麼別的理由來解釋，因為靜動脈位置特殊，口子是橢圓的，兩片就能閉攏。另外三個口子是圓的，要有三片才能閉攏。此外我還要請大家注意，大動脈和動靜脈的組織要比靜動脈和腔靜脈堅硬得多、結實得多，靜動脈和腔靜脈進入心臟前擴大成兩個囊形，稱為心耳，是跟心臟一樣的肌肉構成的；心臟裡的溫度總是高於身體的任何部分；這種溫度可以使流入心臟的血滴立刻膨脹擴張，就像我們把各種液體滴人高溫容器時通常見到的那樣。
I have no need after this to say more to explain the movement of the heart, except that when its cavities are not full of blood, blood necessarily flows from the vena cava into the right cavity and from the arteria venosa into the left; for these two vessels are always full of blood, and their apertures, which open into the heart, cannot then be blocked; but, as soon as two drops of blood have entered the heart in this way, one into each cavity, these drops (which must very great, since the apertures by which they enter are very wide and the vessels from which they come are full of blood) rarify and dilate because of the heat they find there. In this way they cause the whole heart to swell, and they push shut the five little doors which are at the entrances of the two vessels from which they flowed, thus preventing any more blood coming down into the heart. Continuing to become more and more rarified, the drops of blood push open the six other little doors which are at the entrances of the two other vessels through which the blood leaves the heart, causing in this way all the branches of the vena arteriosa and the aortato swell at more or less the same time as the heart.* Immediately afterwards the heart contracts, as do these arteries also, because the blood that has entered them has cooled, and their six little doors shut again; and the five doors of the vena cava and the arteria venosa open again and allow two new quantities of blood to pass through, which immediately cause the heart and the arteries to swell up as before. And because the blood that enters the heart in this way, passes through the two pouches which are called auricles, it follows from this that their movement is the opposite of the heart’s, and that they contract when the heart swells. Finally, so that those who do not know the force of mathematical proof and are not used to distinguish true reasoning from plausible reasoning, should not venture to deny all this without examining it, I would like to point out to them that the movement I have just explained follows necessarily from the mere disposition of organs that one can see with the naked eye in the heart, from the heat which one can feel there with one’s fingers, and from the nature of blood which one can know from observation, in the same way as the movement of a clock follows from the force, position, and shape of its counter weights and wheels.*
注意到這幾點之後，我就用不著說出什麼別的理由來解釋心臟的運動了。要知道，那兩個心腔沒有充滿血液的時候，血液必然要從腔靜脈流人右腔，從靜動脈流入左腔，因為這兩條血管是經常充滿血液的，這時它們朝心臟開的口子又閉不住；可是一流進兩滴血，一個心腔一滴，由於進口開得很大，後面的血管又充滿血液，血滴必然很大，遇到高溫就立刻變稀膨脹，這樣一來，就把整個心臟撐大，把那兩條血管入口上的五扇小門推得閉攏，堵死了來路，心臟裡的血液就不再增多；這兩滴血繼續稀化，越變越稀，就把另外兩條血管口上的六扇小門推開，打通了去路，這樣一來，就幾乎在撐大心臟的同時把動靜脈和大動脈的一切分支全都撐大了；然後心臟就立刻收縮，這兩條動脈也跟著收縮，因為流進來的血液在那裡冷卻了，於是那裡的六扇小門重新閉攏，腔靜脈和靜動脈上的五扇小門重新打開，放進另外兩滴血，這兩滴血又把心臟和動脈撐大，跟前兩滴完全一樣；由於流人心臟的血液先經過那兩個稱為心耳的囊，所以心耳的運動是與心臟的運動正好相反的，心臟舒張的時候心耳就收縮。由於有一些人不明白數學證明的力量，不善於判別真正的推理和似是而非的推理，很可能不作調查研究就貿然否定以上的說法，我願意提醒他們：我剛才說明的心臟運動，是由那種可以用眼睛在心臟裡看到的器官結構必然引起的，是由那種可以用手指在心臟裡摸到的溫度必然引起的，是由那種可以憑經驗認識到的血液本性必然引起的，正如時鐘的運動是由鐘擺和齒輪的力量、位置、形狀必然引起的一樣。
But if one asks why the blood in the veins is not all used up by flowing continually in this way into the heart, and why the arteries are not too full because all the blood which passes through the heart goes into them, I need only repeat the answer already given by an English doctor, who must be praised for having broken the ice on this subject.* He was the first to show that there are many small passages at the extremities of the arteries through which the blood they receive from the heart enters the small branches of the veins, from which it immediately goes back to the heart, so that its course is nothing but a perpetual circulation. He proves this very well from the common experience of surgeons, who, having bound an arm moderately tightly above the point where they open a vein, make the blood flow out more abundantly than if they had not bound the arm. And the opposite would happen if they bound the arm below, between the hand and the vein being opened, or if they bound it very tightly above. For it is obvious that the moderately tight ligature, while being able to prevent the blood that is already in the veins from returning to the heart through the veins, cannot stop on that account fresh blood arriving from the arteries, because they are situated below the veins and their walls, being harder, are less easy to compress; and because the blood coming from the heart tends to flow through the arteries to the hand with greater force than it does when returning from the hand towards the heart through the veins. And because the blood comes out of the arm through the opening in one of the veins, there must necessarily be some passages below the ligature, that is to say, towards the extremities of the arm, through which it can come from the arteries. He also proves very well what he says about the circulation of the blood, first by certain small membranes which are disposed at various points along the veins in such a way that they do not let blood pass from the centre of the body towards its extremities, but only permit it to return from the extremities towards the heart; second, by the experiment that shows that all the blood in the body can flow out of it in a very short space of time by a single artery when it is cut, even if it is tightly bound close to the heart, and cut between the heartand the ligature, so that there is no reason to imagine that the blood that flows out comes from anywhere but the heart.
如果有人問：靜脈裡的血液既然繼續不斷地流人心臟，怎麼不會流幹？既然血液通過心臟都流進了動脈，動脈怎麼不會灌滿？我對這個問題的答覆，無非就是一位英國醫生已經寫過的那些。他應當受到表揚，因為他在這方面打破了悶葫蘆，第一個告訴我們：在動脈的末梢上有許多細微的通道，經過這些通道，從心臟流來的血液就進入靜脈的毛細分支，再重新流向心臟，它的行程只是一個永遠不停的循環。所以說，他用外科醫生的通常經驗作了非常充分的證明：外科醫生切開臂部靜脈放血的時候，如果在切口上方把手臂不松不緊地捆住，血液就出得比不捆多；如果捆在切口下方靠手一邊，或者在上方捆得太緊，情況就完全相反。因為很明顯，在上方不緊不松地捆住可以阻止手臂裡已有的血液通過靜脈回到心臟，並不妨礙血液通過動脈不斷地從心臟回到手臂，這是因為動脈的位置在靜脈底下，管壁又比較硬，不容易壓扁，從心臟向手臂流的動脈血力量又大於從手臂流回心臟的靜脈血；這血既然通過一根靜脈上的切口從手臂裡往外流，那就必定有一些通道位於綑紮處的下方，也就是說，靠近手臂的末端，血液可以從動脈通過那些通道來到切口。他還對他的血液流程學說作了一個非常充分的說明，根據是：有好些細小的皮膜沿著靜脈裝配在不同的地點，使靜脈中的血液不能從身體的中樞往末端流，只能從末端流回心臟；此外還有一個實驗表明，身體裡的全部血液，只要切開一根動脈，就會在很短的時間內流光，雖然這根動脈是在離心臟很近處緊緊結紮住的，切口在心臟與結紮點之間，使我們不至於想像到流出的血液是從別處來的。
But there are many other things which are evidence of the fact that the true cause of this movement of the blood is as I have said it is. First, there is the difference to be observed between the blood which issues from the veins and that which issues from the arteries; this can only be due to the fact that, being rarefied, and, as it were, distilled in passing through the heart, it is thinner, more lively, and hotter straight after leaving it (that is to say, while in the arteries), than it is shortly before entering the heart (that is to say, while in the veins). And if one makes a careful observation, one will find this difference is only clearly perceptible close to the heart and not as perceptible in the parts most distant from it. Next, the hardness of the walls of which the vena arteriosa and the aorta are composed indicates clearly enough that blood beats against these more powerfully than against the veins. And why should the left cavity ofthe heart and the aorta be larger and wider than the right cavity and the vena arteriosa, if not because the blood of the arteria venosa, having been in the lungs only since it left the heart, is thinner and becomes more easily rarefied than the blood which flows directly from the vena cava? And what can physicians find out from taking the pulse if they did not know that, as the nature of blood changes, it can be rarefied by the heat of the heart to a greater or lesser degree and more or less quickly than before? And if we examine how this heat communicates itself to the other members of the body, must we not admit that this happens by means of the blood which is reheated as it passes through the heart and spreads from there throughout the body? From which it follows that, if we remove blood from some part of the body, we remove heat by the same means as well, and even if the heart were as hot as a piece of glowing iron, it would not have sufficient heat to warm up the hands and feet as it does at present, unless it continually sent new blood to them. Then, too, we know from this that the true function of breathing is to bring enough fresh air into the lungs to cause the blood entering them from the right cavity into the heart, where it has been rarefied and, as it were, changed into vapour, to thicken up and convert itself once more into blood, before falling back into the left cavity; if it did not do this, it would not be fit to nourish the fire that is there. All this is confirmed by the fact that we see that animals not having lungs have also only one cavity in the heart, and that unborn children, who cannot use their lungs while in their mother’s womb, have an aperture through which blood flows from the vena cava into the left cavity of the heart, and a duct by which it comes from the vena arteriosa to the aorta, without passing through the lung. And then, how could digestion occur in the stomach, if the heart did not send heat there through the arteries, together with some of the most fluid parts of the blood, which help to dissolve the food that we have ingested? And is it not easy to understand the action which converts the juice of this food into blood, if we consider that the blood is distilled perhaps more than one or two hundred times every day by passing repeatedly through the heart? And what else is needed to explain nutrition and the production of the various humours* present in the body other than to say that the force with which the blood passes, as it rarefies, from the heart to the extremities of the arteries, causes some of its parts to come to rest in the parts of the members in which they then find themselves and there take the place of other parts which they expel; and that, according to the position, shape, or small size of the pores they encounter, some parts of the blood rather than others flow to certain places, in the same way that we see that sieves with different grades of mesh serve to separate different grains from each other? And finally, the most remarkable thing about all this is the generation of animal spirits,* which, like a very subtle* wind, or rather like a very pure and living flame, rise continually in great abundance from the heart to the brain, pass from there through the nerves into the muscles, and impart movement to all our members. We do not need to suppose any other cause to impel the most agitated and the most penetrating parts of the blood (and hence the best suited to compose these spirits) to make their way to the brain rather than anywhere else, than that the arteries that carry them there are those which come most directly from the heart, and that, according to the rules of mechanics (which are the same as those of nature), when many things tend to move together towards the same place in which there is not room for them all (as in the case of the parts of the blood that leave the left cavity of the heart and flow towards the brain), the weaker or less agitated must of necessity be displaced by the stronger, which by this means reach their destination on their own.
可是還有許多別的情況證明，血液運動的真正原因是我所說的那一種。首先，我們看到靜脈血與動脈血有差別，這只能是由於血液經過心臟變稀了，可以說汽化了，它剛流出心臟不久、處在動脈裡的時候，與它進入心臟以前不久、處在靜脈裡的時候相比，要更精細、更活躍、更熱；而且，如果仔細觀察，還可以發現這種差別只是在靠近心臟的地方表現得很顯著，在離開心臟很遠的地方就不那麼顯著了。其次，動靜脈和大動脈的管壁很硬，這就充分表明，血液對這兩條血管的衝擊要比對靜脈的衝擊更有力；心臟左腔和大動脈之所以比右腔和靜動脈寬大，只是由於靜動脈裡的血液通過心臟後僅僅在肺裡待過，要比剛從腔靜脈裡的血液更精細，稀化得更厲害、更迅速。醫生之所以能夠切脈診斷，只是由於他知道，血液的性質改變了，心臟溫度使血液稀化的強度和速度就會發生變化。如果我們研究心臟的溫度是怎樣傳到其他肢體上去的，那就必須承認這是憑藉血液，血液經過心臟變熱，再從那裡帶著溫度流到全身；因此，如果把身體上某個部分的血弄掉，那個部分也就變涼了；心臟儘管燙得像一塊燒紅的鐵，如果不把新的血液不斷輸送到手腳上去，還是不足以使手腳變熱的。我們又由此認識到，呼吸的真正用途就在於往肺裡運送足夠的新鮮空氣，血液在心臟裡已經稀化成為蒸汽，從右腔進人兩肺，遇到空氣就濃縮起來，重新變成血液，然後回到左腔，這樣才能給那裡的火當燃料。這是很可靠的，因為我們看到，沒有肺的動物心臟就只有一個腔；胎兒在母腹中不能用肺，腔靜脈的血液就通過一個口子流入左心腔，又從動靜脈通過一根管子流人大動脈，並不經過肺。此外，消化之所以能在胃裡進行，只是由於心臟通過動脈把溫度輸送到胃裡，同時還送去一些流動性較大的血液分子，幫助分解吃進的肉食。如果考慮到血液反覆經過心臟化為蒸汽每天大約不下一二百次，那就很容易了解那種使肉食漿汁轉化為血液的作用了。我們也不用舉出什麼別的情況來說明營養是怎麼一回事，各種不同的體液是怎樣產生的，只需要說：血液稀化時帶著一股力量，從心臟向動脈的末梢推進，在達到各個器官的時候，血液中的某些分子就在那裡停留下來，把器官中的一些分子趕跑，取而代之；由於遇到的孔隙位置不同、形狀不同、大小不同，所以有一些血液分子鑽得進，有一些鑽不進去，就像一些型號不同的篩子，打著各式各樣的眼，可以把不同種類的穀粒分開一樣。最後是這一切中間最值得注意的一種現象，即元氣的產生：元氣好像一股非常精細的風，更像一團非常純淨、非常活躍的火，不斷地、大量地從心臟向大腦上升，從大腦通過神經鑽進肌肉，使一切肢體運動；這就用不著再設想什麼別的原因來說明，為什麼那些最靈活、最敏銳的血液分子最適宜於構成元氣，只往大腦裡鑽，不往別處去，這只是因為從心臟輸送它們到大腦去的動脈是最直的，只是因為按照機械學的規律（自然界的規律也是一樣），如果有好多東西同時往一處擠，那裡又沒有足夠的地方把它們都容下（那些血液分子從左心腔往大腦擠的情況就是這樣），有力的就必定把軟弱的、不靈活的擠到一邊，獨佔鰲頭。
I had explained all these matters in considerable detail in the treatise which I had earlier intended to publish.* And I had then shown what structure the nerves and the muscles of the human body must have to enable the animal spirits, being inside that body, to have the power to move its members, as we observe in the case of severed heads, which we can see moving and biting the earth shortly after having been cut off, although they are no longer animate. I had also shown what changes must occur in the brain to cause states of waking, sleeping, and dreaming; how light, sounds, smells, tastes, heat, and all the other qualities of external objects can imprint various ideas on the brain through the intermediary of the senses; how hunger, thirst, and the other internal passions can also transmit ideas to the brain; what must be taken to be the sensus communis* in which these are received, the memory which preserves them, and the faculty of imagination, which can change them in different ways, form them into new ideas and, by the same means, distribute animal spirits to the muscles and make the members of this body move, with respect both to the objects which present themselves to the senses and to the internal passions, in as many different ways as the parts of our bodies can move without being directed by our will. This will not appear at all strange to those who know how wide arange of different automata or moving machines the skill of man can make using only very few parts, in comparison to the great number of bones, muscles, nerves, arteries, veins, and all the other parts which are in the body of every animal. For they will consider this body as a machine which, having been made by the hand of God, is incomparably better ordered and has in itself more amazing movements than any that can be created by men.
我在曾經打算發表的那部論著裡對這一切作了相當詳細的說明。接著我又在那部書裡指出：人身上的神經和肌肉一定要構造成什麼樣子，其中的元氣才能夠使肢體運動，就像我們見到的那樣，腦袋砍下之後不久，儘管已經不是活的，還在動來動去，亂啃地皮；大腦裡一定要發生什麼樣的變化，才能使人清醒、睡眠和做夢；光亮、聲音、香氣、滋味、溫度以及屬於外界對象的性質，怎樣能夠通過感官在大腦裡印上各種不同的觀念；饑渴等等內心感受又怎樣能夠把它們的觀念送進大腦；通覺怎樣接納這些觀念，記憶怎樣保存這些觀念，幻想怎樣能夠把這些觀念改頭換面、張冠李戴拼湊成新的觀念，並且用這樣的辦法把元氣布置在肌肉裡，使這個身體上的肢體做出各式各樣的動作，既有關於感官對象方面的，也有關於內心感受方面的，就像我們的肢體那樣，沒有意志指揮也能動作。在我們看來這是一點都不奇怪的，我們知道人的技巧可以做出各式各樣的自動機，即自己動作的機器，用的只是幾個零件，與動物身上的大量骨骼、肌肉、神經、動脈、靜脈等等相比，實在很少很少，所以我們把這個身體看成一臺神造的機器，安排得十分巧妙，做出的動作十分驚人，人所能發明的任何機器都不能與它相比。講到了這裡，我又特意停下來指出：如果有那麼一些機器，其部件的外形跟猴子或某種無理性動物一模一樣，我們是根本無法知道它們的本性與這些動物有什麼不同的；可是如果有一些機器跟我們的身體一模一樣，並且儘可能不走樣地模仿著我們的動作，我們還是有兩條非常可靠的標準，可以用來判明它們並不因此就是真正的人。第一條是：它們決不能像我們這樣使用語言，或者使用其他由語言構成的訊號，向別人表達自己的思想。因為我們完全可以設想一臺機器，構造得能夠吐出幾個字來，甚至能夠吐出某些字來回答我們扳動它的某些部件的身體動作，例如在某處一按它就說出我們要它說的要求，在另一處一按它就喊痛之類，可是它決不能把這些字排成別的樣式適當地回答人家向它說的意思，而這是最愚蠢的人都能辦到的。第二條是：那些機器雖然可以做許多事情，做得跟我們每個人一樣好，甚至更好，卻決不能做別的事情。從這一點可以看出，它們的活動所依靠的並不是認識，而只是它們的部件結構；因為理性是萬能的工具，可以用於一切場合，那些部件則不然，一種特殊結構只能做一種特殊動作。由此可見，一臺機器實際上決不可能有那麼多的部件使它在生活上的各種場合全都應付裕如，跟我們依靠理性行事一樣。而且，依靠這兩條標準我們還可以認識人跟禽獸的區別。因為我們不能不密切注意到：人不管多麼魯鈍、多麼愚笨，連白痴也不例外，總能把不同的字眼排在一起編成一些話，用來向別人表達自己的思想；可是其他的動物相反，不管多麼完滿，多麼得天獨厚，全都不能這樣做。這並不是由於它們缺少器官，因為我們知道，八哥和鸚鵡都能像我們這樣吐字，卻不能像我們這樣說話，也就是說，不能證明它們說的是心裡的意思；可是先天聾啞的人則不然，他們缺少跟別人說話的器官，在這一點上跟禽獸一樣，甚至不如禽獸，卻總是自己創造出一些手勢把心裡的意思傳達給那些跟他們常在一起並且有空學習他們這種語言的人。這就證明禽獸並非只是理性不如人，而是根本沒有理性，因為學會說話是用不著多少理性的；我們雖然看到那些同種的動物也跟人一樣彼此能力不齊，有比較容易訓練的，有比較笨的，可是最完滿的猴子或鸚鵡在學話方面卻比不上最笨的小孩，連精神失常的小孩都比不上；如果不是動物的靈魂在本性上跟我們完全不同，這是無法想像的。我們決不能把語言與表現感情的自然動作混為一談，那些動作動物是可以模仿的，機器也同樣可以模仿；我們也不能像某些古人那樣，認為禽獸也有語言，只是我們聽不懂。因為如果真是這樣，禽獸既然有許多器官跟我們相似，它們就能夠向我們表達思想，如同向它們的同類表達一樣了。還有一件事非常值得注意，這就是：雖然有許多動物在它們的某些活動上表現得比我們靈巧，可是我們看到，儘管如此，這些動物在許多別的事情上卻並不靈巧：它們做得比我們好並不證明它們有心思；因為它們假如有就會比我們任何人都強，就會在一切其他事情上做得都好；可是它們並沒有心思，是它們身上器官裝配的本性起的作用：正如我們看到一架時鐘由齒輪和發條組成，就能指示鐘點、衡量時間，做得比我們這些非常審慎的人還要準確。
Following this, I had described the rational soul, and shown that, unlike the other things of which I had spoken, it could not possibly be derived from the potentiality of matter, but that it must have been created expressly. And I had shown how it is not sufficient for it to be lodged in the human body like a pilot in his ship, *except perhaps to move its members, but that it needs to be more closely joined and united with the body in order to have, in addition, feelings* and appetites like the ones we have, and in this way compose a true man. I dwelt a little at this point on the subject of the soul, because it is of the greatest importance. For, after the error of those who deny the existence of God, which I believe I have adequately refuted above, there is none which causes weak minds to stray more readily from the narrow path of virtue than that of imagining that the souls of animals are of the same nature as our own, and that, as a consequence, we have nothing more to fear or to hope for after this present life, any more than flies and ants. But when we know how different flies and ants are, we can understand much better the arguments which prove that our soul is of a nature entirely independent of the body, and that, as a consequence, it is not subject to death as the body is. And given that we cannot see any other causes which may destroy the soul, we are naturally led to conclude that it is immortal.*
這以後我還描述了理性靈魂，表明它決不能來自物質的力量，跟我所說的其他事情一樣，正好相反，它顯然應當是神創造出來的；我們不能光說它住在人的身體裡面，就像舵手住在船上似的，否則就不能使身體上的肢體運動，那是不夠的，它必須更加緊密地與身體聯成一氣，才能在運動以外還有同我們一樣的感情和欲望，這才構成一個真正的人。然後，我在這裡對靈魂問題稍微多談幾句，因為這是最重要的一個問題。要知道，無神論的錯誤我在上面大概已經駁斥得差不多了，可是此外還有一種錯誤，最能使不堅定的人離開道德正路，就是以為禽獸的靈魂跟我們的靈魂本性相同，因而以為我們跟蒼蠅、螞蟻一樣，對身後的事情沒有什麼可畏懼的，也沒有什麼可希望的；反過來，知道我們的靈魂跟禽獸的靈魂大不相同，也就更加明白地了解，為什麼我們的靈魂具有一種完全不依賴身體的本性，因而決不會與身體同死；然後，既然看不到什麼別的原因使它毀滅，也就很自然地由此得出結論，斷定它是不會死的了。
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RENÉ DESCARTES A Discourse on the Method of Correctly Conducting One’s Reason and Seeking Truth in the Sciences. Oxford University Press Inc.
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