2.2 Autopoiesis理論的正式描述

    目前,，我已經(jīng)對(duì)整個(gè)思想有了一個(gè)大致的描述,，這一節(jié)開(kāi)始更加詳細(xì)的描述Maturana和Varela的理論細(xì)節(jié)。
我們觀察到：所有的描述和解釋都是來(lái)源于觀察者,，他（她）把一個(gè)實(shí)體或者一種現(xiàn)象從背景中區(qū)分出來(lái),。這種描述往往部分依賴于觀察者的選擇和觀察過(guò)程，而且或多或少都會(huì)對(duì)被觀察對(duì)象的實(shí)際行為造成影響,。
    Maturana把一個(gè)能被觀察者從背景中區(qū)分出來(lái)的整體稱為一個(gè)實(shí)體,。例如，當(dāng)我們稱某物為汽車的時(shí)候,，一些屬性或者預(yù)定義的特征就被指定上去 了（如它是可以移動(dòng)的,，可以載人，可駕駛的等等）,。觀察者還可以進(jìn)一步把一個(gè)實(shí)體分解成多個(gè)單元和單元之間的關(guān)系,，這種方法雖然不同但是仍然可以非常有效 的來(lái)指定實(shí)體。它的結(jié)果就是把一個(gè)由多個(gè)部件構(gòu)成的實(shí)體描述為一個(gè)整體的組織,。
    Maturana和Varela還特別強(qiáng)調(diào)區(qū)分實(shí)體的組織和實(shí)體的結(jié)構(gòu)：
[組織]是指一種發(fā)生于部件之間的抽象關(guān)系,。通過(guò)指定一個(gè)區(qū)域，組織在其中發(fā)生相互作用,，并被賦予了不可分解的整體屬性,。組織這種關(guān)系定義了一個(gè)包含了某種特定類別組件的實(shí)體系統(tǒng)，并且決定了該實(shí)體的抽象屬性,。
[結(jié)構(gòu)]是指實(shí)際的構(gòu)成部件以及它們之間的實(shí)際關(guān)系,。這些部件和關(guān)系必須滿足于他們所屬的合成實(shí)體的組織抽象關(guān)系，并且決定了一個(gè)發(fā)生部件之間的相互作用 而擾動(dòng)的空間區(qū)域,，但是結(jié)構(gòu)沒(méi)有決定它作為一個(gè)實(shí)體應(yīng)該具有哪些屬性,。
（譯者注：與我們的理解正相反，組織相當(dāng)于抽象的類,，而結(jié)構(gòu)是指該類的一種特定實(shí)例）

    組織包含了部件之間的關(guān)系以及為了刻畫實(shí)體術(shù)語(yǔ)某種特定類別部件所必需具備的性質(zhì),。這就決定了它的屬性是作為一個(gè)整體的,。我們可以用正方形的概念來(lái)說(shuō)明組 織。一個(gè)正方形用空間上部件之間的相互關(guān)系定義,，正方形就是一個(gè)有四個(gè)相等邊,、并且用直角連接在一起的圖形。這里正方形就是組織,，而任何一個(gè)實(shí)現(xiàn)正方形的 物理方式都是一種能夠?qū)崿F(xiàn)這種抽象組織的特定結(jié)構(gòu),。另外一個(gè)例子就是飛機(jī)，它可以被定義為若干部件,，如翅膀,、引擎、控制器,、剎車器,、座椅而且這些部件之間 的關(guān)系使得飛機(jī)可以飛起來(lái)。如果一個(gè)實(shí)體擁有這樣的組織,，那么他就會(huì)被定義為一個(gè)飛機(jī),，因?yàn)樗梢援a(chǎn)生我們對(duì)于飛機(jī)這個(gè)整體所期望的屬性。另一方面,，飛機(jī) 的結(jié)構(gòu)描述了任意一個(gè)包含實(shí)際的部件和實(shí)際的關(guān)系的實(shí)現(xiàn),，例如機(jī)場(chǎng)跑道上的波音757。
    的確,，這種使用術(shù)語(yǔ)“結(jié)構(gòu)”的方法與通常有很大不同,。一般的，在對(duì)系統(tǒng)的描述中,，結(jié)構(gòu)是與那些不發(fā)生緩慢變化的過(guò)程相對(duì)比的概念,，結(jié)構(gòu)和組織幾乎是可以互 換的。而這里,，結(jié)構(gòu)既指靜態(tài)的也指動(dòng)態(tài)的元素,。結(jié)構(gòu)和組織的差別僅僅是具體事例和所有實(shí)例背后的抽象普遍性相比較而言的,。這使我們想起了經(jīng)典的結(jié)構(gòu)主義哲 學(xué),，它們把表面上的經(jīng)驗(yàn)事件“結(jié)構(gòu)”與一個(gè)不可觀察到的可以生成這種表面結(jié)構(gòu)的深層結(jié)構(gòu)（“組織”）相關(guān)起來(lái)。
    因此,，任何一個(gè)存在的合成實(shí)體都同時(shí)具有結(jié)構(gòu)和組織,。有很多種不同的結(jié)構(gòu)可以實(shí)現(xiàn)同樣的組織，并且每一種結(jié)構(gòu)都會(huì)有很多屬性和相互作用是不能被組織來(lái)指定 的,，也是與組織不相關(guān)的,。例如，一個(gè)飛機(jī)的形狀,、顏色,、尺寸和材質(zhì)。進(jìn)一步，結(jié)構(gòu)可以在沒(méi)有組織更改的條件下改變或被改變,。例如,，對(duì)于經(jīng)歷了很長(zhǎng)時(shí)間的飛 機(jī)來(lái)說(shuō)，它有新組裝的部件,、涂了新漆,，但它還是一個(gè)飛機(jī)因?yàn)樗牡讓咏M織沒(méi)有變化。然而,，有一些改變就會(huì)破壞組織的存在,，例如，一次撞擊事故把飛機(jī)變成了 殘骸,。
    結(jié)構(gòu)和組織的本質(zhì)區(qū)別就是整體與部分的區(qū)別,。飛機(jī)只有在作為一個(gè)整體的時(shí)候才能夠飛起來(lái)。這是它作為一個(gè)整體組成的屬性,，是它的組織,。然而，它的部分,，可 以依賴于它的所有屬性在它自身的領(lǐng)域中與其他部分進(jìn)行相互作用,，然而，它們僅僅作為一個(gè)個(gè)體的部件來(lái)這樣完成,。與一只小鳥(niǎo)相撞會(huì)使得引擎停止,；一個(gè)線路短 路可以毀掉整個(gè)控制。這些都是對(duì)于結(jié)構(gòu)的干擾,，也許這種擾動(dòng)可以導(dǎo)致整個(gè)結(jié)構(gòu)的破壞和消失,，也可能是可以彌補(bǔ)的，以至于飛機(jī)仍然能正常飛行,。
    在這種背景下,，我們可以很好的理解Maturana和Varela對(duì)Autopoiesis理論的定義了。一個(gè)實(shí)體是通過(guò)定義實(shí)體隸屬于某個(gè)類別的組織來(lái) 刻畫的,，并且組織決定了該實(shí)體所能產(chǎn)生的外在表現(xiàn),。Maturana和Varela把生命系統(tǒng)的本質(zhì)看作是動(dòng)態(tài)的和自主的，并且認(rèn)為自我生產(chǎn)是產(chǎn)生這些特 性的本質(zhì)原因,。因此,，生命的組織就是一種自我產(chǎn)生的系統(tǒng)—Autopoeisis。這種組織當(dāng)然可以被無(wú)窮多的結(jié)構(gòu)來(lái)實(shí)現(xiàn),。

    對(duì)自創(chuàng)生系統(tǒng)的一個(gè)更加明確的定義是：一個(gè)動(dòng)態(tài)的系統(tǒng),，它是一個(gè)由部件生成的網(wǎng)絡(luò)合成的實(shí)體，該實(shí)體滿足：
a) 通過(guò)相互作用迭代的再生產(chǎn)產(chǎn)生它們自己的網(wǎng)絡(luò)
b) 用一個(gè)空間上的實(shí)體來(lái)實(shí)現(xiàn)這個(gè)網(wǎng)絡(luò),。該實(shí)體要能產(chǎn)生出與它所在的相互作用的背景分離的邊界,。

     這段引文的第一部分詳細(xì)敘述了自我生產(chǎn)系統(tǒng)的一般思想,，第二部分則特別指定了系統(tǒng)必須被實(shí)際認(rèn)出是一個(gè)整體，并且它的邊界也是系統(tǒng)自己產(chǎn)生的,。關(guān)于第二點(diǎn) 產(chǎn)生邊界很重要,，尤其是當(dāng)人們把自創(chuàng)生理論應(yīng)用到其他非生命領(lǐng)域例如社會(huì)的時(shí)候。雖然對(duì)于細(xì)胞來(lái)說(shuō)是該定義是非常清晰的,，但是這個(gè)定義本身并沒(méi)有限定系統(tǒng) 的實(shí)現(xiàn)一定是物理的實(shí)體,。這就使得該思想是開(kāi)放的并且可以討論一些非常抽象的自創(chuàng)生系統(tǒng)，例如一組概念,，一個(gè)細(xì)胞自動(dòng)機(jī),，或者是一個(gè)通訊的過(guò)程。對(duì)于這類 抽象的系統(tǒng)來(lái)說(shuō)什么是它們的邊界呢,？我們真的能把這類系統(tǒng)稱為是“活的”么,？事實(shí)上，這個(gè)主題是非常有爭(zhēng)議的,，詳細(xì)請(qǐng)看第3.3.2節(jié),。
     當(dāng)我們考慮自然中的組織的時(shí)候，這個(gè)有些空乏的概念還可以得到進(jìn)一步地?cái)U(kuò)展,。特別是,，組織將會(huì)涉及到部件之間的關(guān)系。根據(jù)Maturana和Varela 的理論,，在物理系統(tǒng)中,，這種關(guān)系必然是三個(gè)種類之一：構(gòu)造（Constitution），特化（Specification）和順序(Order),。構(gòu)造 關(guān)系是一種系統(tǒng)上的物理學(xué)拓?fù)潢P(guān)系,，也就是它的三維幾何形體（比如一個(gè)細(xì)胞）。例如,，他們都有細(xì)胞膜,，各個(gè)部件都保持著特定的相對(duì)距離，它們都具有需要的 尺寸和形狀,。特化關(guān)系決定了被各種構(gòu)建過(guò)程生產(chǎn)的部件必須保持自創(chuàng)生的連續(xù)性,。最后，順序關(guān)系與過(guò)程的動(dòng)態(tài)有關(guān),。例如,，各種分子的適當(dāng)配量是在正確的時(shí)間 以正確的頻率生產(chǎn)出來(lái)的。關(guān)于這些關(guān)系的具體細(xì)節(jié)將在后面論述,，然而我們清楚的是，“何處”,、“什么”,、“何時(shí)”細(xì)胞中發(fā)生了各種復(fù)雜的生產(chǎn)過(guò)程已經(jīng)被這 三種關(guān)系粗糙的說(shuō)明了,。
     對(duì)于這類“自創(chuàng)生”必需要關(guān)系的描述似乎有那么一些目的論的意味。事實(shí)上并不是這樣的,，Maturana和Varela非常強(qiáng)烈的反對(duì)這種解釋,。的確，如 果這樣的部件和關(guān)系發(fā)生了,，那么它們就會(huì)使得電化學(xué)過(guò)程自己生產(chǎn)自己,，并且在正確的頻率下，生產(chǎn)正確的類型構(gòu)造出一個(gè)自創(chuàng)生的系統(tǒng),。但事實(shí)上,，這并不是必 需的。因?yàn)檫@樣簡(jiǎn)單的組合也許發(fā)生也許不發(fā)生,，這就像植物生長(zhǎng)也許依靠水,、光和營(yíng)養(yǎng)的正確組合，也許并不依靠一樣,。
    為了使早期的這些抽象特征更具有可操作性,，Varela在1974年的時(shí)候開(kāi)發(fā)了一個(gè)自創(chuàng)生的細(xì)胞自動(dòng)機(jī)模型，并提出了辨別自創(chuàng)生系統(tǒng)的六個(gè)關(guān)鍵點(diǎn),，它們是：
i) 通過(guò)相互作用決定實(shí)體是否具有一個(gè)可區(qū)分的邊界,。如果可以區(qū)分出邊界，則繼續(xù)第2個(gè)步驟,。如果沒(méi)有,，那么實(shí)體就是不可描述的，因此我們也沒(méi)有什么可說(shuō)的,。
ii) 如果實(shí)體有組成的元素,，也就是實(shí)體的部件，這些部件是可以描述的,，那么就進(jìn)入第3步，否則實(shí)體是一個(gè)不可分析的整體因此也不是一個(gè)自創(chuàng)生的系統(tǒng),。
iii) 判斷實(shí)體是否為一個(gè)機(jī)械的系統(tǒng),，也就是系統(tǒng)的屬性要能滿足一定的關(guān)系，該關(guān)系決定了在實(shí)體中部件的交互和轉(zhuǎn)換,。如果這種情況滿足,，則跳到第4步，否則該實(shí)體不是一個(gè)自創(chuàng)生的系統(tǒng),。
iv) 判斷實(shí)體邊界的組成元素和它們之間的關(guān)系是通過(guò)“近鄰偏好相互作用”以及該實(shí)體所在的空間的屬性來(lái)決定的,。（譯者注：這里的所謂近鄰偏好相互作用 preferential neighborhood interaction是指部件僅僅與它附近的局部元素發(fā)生相互作用而不是某種整體宏觀的相互作用，就好比所有的人工生命模型一樣,，每個(gè)生命僅僅考慮它的 局部環(huán)境而不失全局）,，如果不是這樣,，那么你沒(méi)有得到一個(gè)自創(chuàng)生的實(shí)體，因?yàn)橄到y(tǒng)的邊界不是由它自身決定的,，而是由外界得到的,。如果實(shí)體滿足條件4，那么 就跳到條件5
v) 判斷實(shí)體的邊界是否由實(shí)體內(nèi)的相互作用產(chǎn)生的,，或者通過(guò)產(chǎn)生的部件轉(zhuǎn)換構(gòu)成了邊界,，或者是那些進(jìn)入組織邊界的元素通過(guò)耦合轉(zhuǎn)化構(gòu)成的。如果這些情況都不是,，那么這就不是一個(gè)自創(chuàng)生實(shí)體,。如果滿足跳到下一步
vi) 如果實(shí)體內(nèi)的其他部件也是如第5步中的那樣由部件之間的相互作用產(chǎn)生的，同時(shí),，雖然有些部件并不是由實(shí)體內(nèi)部組件通過(guò)相互作用產(chǎn)生的,，但是卻參與了其他構(gòu) 成部件的必要而持久的生產(chǎn)過(guò)程，那么你就在部件存在的空間中得到了一個(gè)自創(chuàng)生的實(shí)體,。如果不滿足這些情況,，也就是系統(tǒng)內(nèi)的部件并不是像5那樣由系統(tǒng)內(nèi)部的 其他部件生成的，那么你并沒(méi)有得到一個(gè)自創(chuàng)生的實(shí)體,。
     前三個(gè)標(biāo)準(zhǔn)是非常普遍的,，它強(qiáng)調(diào)用一個(gè)清晰的邊界定義了一個(gè)可分辨的整體，并且這個(gè)實(shí)體可以被分解成若干部件,，而且實(shí)體操作這些組件是一種機(jī)械的過(guò)程,，也 就是說(shuō)這些過(guò)程都是由部件的屬性和關(guān)系決定的。自創(chuàng)生思想的核心是最后的三條,。這些標(biāo)準(zhǔn)描述了一個(gè)交互過(guò)程和生產(chǎn)過(guò)程的動(dòng)態(tài)網(wǎng)絡(luò)(vi),，它產(chǎn)生了邊界 (v)，并且這個(gè)邊界被組件之間的“近鄰偏好相互作用”所維護(hù),。關(guān)鍵的一個(gè)概念就是部件的生產(chǎn),，而且生產(chǎn)的這些部件構(gòu)成了邊界。尤其是當(dāng)我們把自創(chuàng)生理論 擴(kuò)展到非物理系統(tǒng)的時(shí)候顯得尤為重要,。
    我們將把這些評(píng)價(jià)標(biāo)準(zhǔn)應(yīng)用到細(xì)胞身上,。在這里我們將簡(jiǎn)要的描述自創(chuàng)生關(guān)系的實(shí)現(xiàn)，以及通過(guò)應(yīng)用分子生物學(xué)中描述的細(xì)胞的構(gòu)成,，正如Alberts或Freifelder,，Raven和Johnson等人介紹的。

2.3 細(xì)胞中的自創(chuàng)生過(guò)程說(shuō)明

    這一節(jié)將簡(jiǎn)單描述一個(gè)細(xì)胞中的化學(xué)物質(zhì)自創(chuàng)生關(guān)系,。Alberts等人曾經(jīng)作過(guò)很好的有關(guān)分子生物學(xué)的介紹,。
2.3.1 應(yīng)用六個(gè)標(biāo)準(zhǔn)
     Zeleny和Hufford曾經(jīng)對(duì)一個(gè)典型的細(xì)胞從六個(gè)關(guān)鍵點(diǎn)進(jìn)行了分析，兩種細(xì)胞的示意圖如下圖所示，其中一個(gè)是真核細(xì)胞,，也就是細(xì)胞內(nèi)有細(xì)胞核的,，另一個(gè)是原核細(xì)胞,，其中沒(méi)有細(xì)胞核,。

1. 細(xì)胞擁有可以確認(rèn)的由離子形成的細(xì)胞膜邊界，因此細(xì)胞是明確的實(shí)體,。
2. 細(xì)胞擁有明確的部件,，例如線粒體、細(xì)胞核以及由眾所周知的內(nèi)置網(wǎng)形成的細(xì)胞膜網(wǎng)絡(luò),。所以,，細(xì)胞是可以被分析的。
3. 所有的部件都擁有電化學(xué)屬性,，通用的物理規(guī)律決定了細(xì)胞內(nèi)部部件之間的傳輸和相互作用,。因此，細(xì)胞是一個(gè)機(jī)械的系統(tǒng),。
4. 細(xì) 胞的邊界是由磷脂分子和特定的蛋白質(zhì)合成的細(xì)胞膜構(gòu)成,。脂肪分子排列形成了雙層結(jié)構(gòu)，這種結(jié)構(gòu)就可以形成選擇性的滲透障礙,，蛋白質(zhì)在這種雙層結(jié)構(gòu)中也呈現(xiàn) 膜狀,，調(diào)節(jié)形成了很多細(xì)胞膜的功能。一個(gè)脂肪分子有兩個(gè)部分,，一個(gè)具有極性的頭是親水的,，和一個(gè)碳?xì)浠衔锏奈舶褪菂捤摹Ｎ舶秃皖^連接在一起形成了雙層 結(jié)構(gòu),。完整的蛋白質(zhì)也有吸水和厭水的區(qū)域,，因此邊界部分就通過(guò)近鄰偏好關(guān)系而形成了自我修復(fù)的機(jī)制。
5. 邊界的脂肪和蛋白質(zhì)部件是由細(xì)胞自己產(chǎn)生的,。例如,，大多數(shù)用于形成新的細(xì)胞膜的脂肪分子是由內(nèi)置網(wǎng)形成的，而內(nèi)置網(wǎng)是細(xì)胞的一個(gè)復(fù)雜的,、膜狀的部件,。因此，邊界部件是由系統(tǒng)自我產(chǎn)生的,。
6. 細(xì)胞中的所有其他部件（包括線粒體,、細(xì)胞核、核糖酶素,、內(nèi)置網(wǎng)）都是被細(xì)胞以及在細(xì)胞內(nèi)部產(chǎn)生的,。一些化學(xué)成分（例如金屬離子）不是被細(xì)胞產(chǎn)生的，而是通過(guò)細(xì)胞膜從外界輸入進(jìn)來(lái)的,，但成為了細(xì)胞的操作部分,，所以細(xì)胞的部件是自我生產(chǎn)的,。

2.3.2 構(gòu)造、特化和順序的自創(chuàng)生關(guān)系
     除了六個(gè)標(biāo)準(zhǔn)以外,，自創(chuàng)生理論還定義了三種必要的關(guān)系類型,，下面針對(duì)一個(gè)典型的細(xì)胞來(lái)說(shuō)明這些關(guān)系。
2.3.2.1 構(gòu)造關(guān)系
    構(gòu)造關(guān)系決定了細(xì)胞的三維形狀和結(jié)構(gòu)以便生產(chǎn)的其他關(guān)系可以被維護(hù),。這種關(guān)系是通過(guò)那些具備立體化學(xué)特性的分子并能夠使得其他過(guò)程持續(xù)發(fā)生的分子來(lái)實(shí)現(xiàn)的,。
    一個(gè)明顯的例子就是細(xì)胞膜或者細(xì)胞邊界的構(gòu)建。在動(dòng)物細(xì)胞中,，細(xì)胞膜是圍繞著線粒體的,，就像是圍繞著細(xì)胞自己，它維護(hù)了細(xì)胞內(nèi)的物質(zhì)并且通過(guò)擴(kuò)散而調(diào)節(jié)反 應(yīng)的速率,。各種各樣的反應(yīng)分子沿著細(xì)胞膜按照一種特定的順序分布著,，以便能量生產(chǎn)能夠有序而高效的完成。在植物細(xì)胞中,，除了離子構(gòu)成的細(xì)胞膜以外,，還有一 個(gè)包含了纖維素的細(xì)胞壁。這種纖維素是由葡萄糖物質(zhì)長(zhǎng)鏈包裹在一起而形成的鋼硬的線,，這就形成了植物的剛性,。
    第二個(gè)例子是蛋白質(zhì)酶的活動(dòng)位穴。這些活動(dòng)位穴對(duì)于大部分反應(yīng)來(lái)說(shuō)起著催化劑的作用,，它們能改變特定的物質(zhì)而使得化學(xué)反應(yīng)更容易發(fā)生,。一般的，活 動(dòng)位穴存在于酶分子的特定位置,。在這些位置上,，氨基酸又是通過(guò)“催化劑”或者“合作酶”的幫助利用它結(jié)構(gòu)的配置來(lái)適應(yīng)特定的物質(zhì)。物質(zhì)分子和活動(dòng)位穴相互 鎖定,，只有當(dāng)它們不再適應(yīng)的時(shí)候才會(huì)改變,。

2.3.2.2 特化關(guān)系
    在化學(xué)特性上，這些關(guān)系決定了細(xì)胞組件的唯一性,。這種關(guān)系促使細(xì)胞組件通過(guò)它們之間的相互作用參與了整個(gè)細(xì)胞的構(gòu)建,。在DNA和RNA以及組建產(chǎn)生的介于酶和酶催化的物質(zhì)之間的蛋白質(zhì)中有兩種主要的結(jié)構(gòu)對(duì)應(yīng)。
    蛋白質(zhì)合成是很復(fù)雜的過(guò)程,，因?yàn)槊恳环N蛋白的形成都需要連接20種不同的氨基酸以形成特定的組合,，總計(jì)大概需要300或更多的單元。這就需要RNA模板分子,，就好像每個(gè)蛋白質(zhì)的裁縫一樣,，它按照順序包含了對(duì)每個(gè)氨基酸以及酶和t-RNA的特定空間。
    正如已經(jīng)論述的，酶對(duì)于細(xì)胞中的大多數(shù)反應(yīng)都是必要的,，另外,，每一種特定的反應(yīng)都需要特定的酶以及相應(yīng)的物質(zhì)。因此細(xì)胞需要上百種的酶,，每一種都是由細(xì)胞自己生產(chǎn)的,。

2.3.2.3 順序關(guān)系
    順序關(guān)系涉及了細(xì)胞生產(chǎn)過(guò)程的動(dòng)態(tài)。各種化學(xué)反應(yīng)形成復(fù)雜的反饋閉環(huán)以保證各種產(chǎn)物的生產(chǎn)能夠以正確的速率和順序繼續(xù),。例如,，氧化反應(yīng)的能量生產(chǎn)是在線粒 體中被磷酸鹽和ADP控制的,。同時(shí),，化學(xué)反應(yīng)消耗能量來(lái)生產(chǎn)ADP和磷酸鹽，這樣就可以使得整個(gè)過(guò)程自動(dòng)化,。并且,，能量的高效利用就可以使得這些必要物質(zhì) 的生產(chǎn)更加高效。

2.3.3 其他可能的自創(chuàng)生系統(tǒng)
     一個(gè)非常有趣的問(wèn)題是,，自創(chuàng)生系統(tǒng)是否有其他的實(shí)例呢,？例如，多細(xì)胞生命是不是也是自創(chuàng)生系統(tǒng)呢,？Maturana關(guān)于這個(gè)問(wèn)題的判斷是模棱兩可的,，他懷 疑類似動(dòng)物和植物這樣的生物是二級(jí)自創(chuàng)生系統(tǒng)。也就是它們的組件不是細(xì)胞中的那些分子而是細(xì)胞本身,。另外,，他也建議一些細(xì)胞系統(tǒng)并不是真正的自創(chuàng)生系統(tǒng)， 而僅僅是群落,。那么關(guān)于那些存在著閉圈的組織關(guān)系系統(tǒng),，但人們并不認(rèn)為是生命的系統(tǒng)是否為自創(chuàng)生的呢？最后,，非物理系統(tǒng)例如自創(chuàng)生自動(dòng)機(jī)以及一群思想或者 一個(gè)社會(huì)是否為自創(chuàng)生系統(tǒng)呢,？

2.4．自創(chuàng)生理論在生物和化學(xué)中的應(yīng)用

     讀者一定認(rèn)為正如自創(chuàng)生理論所聲名的，它應(yīng)該在生物學(xué)領(lǐng)域起到關(guān)鍵作用,。而事實(shí)上,，生物學(xué)界接受這個(gè)觀點(diǎn)卻用了很多年的時(shí)間。在1979年的時(shí)候,，我曾經(jīng) 給英國(guó)的著名生物學(xué)家Steven Rose教授寫信尋問(wèn)自創(chuàng)生理論的情況,。他回信說(shuō)雖然Maturana是一個(gè)值得尊敬的生物學(xué)家，但是他不想對(duì)這個(gè)理論作出評(píng)價(jià),。生物學(xué)界有一個(gè)例外是 Lynn Margulis,，她提出了原核生命是由很多更簡(jiǎn)單的生命共生而形成的，這個(gè)理論本身也是備受爭(zhēng)議的。
    然而,，隨著生命的起源以及能夠展現(xiàn)自創(chuàng)生特征的非生命化學(xué)系統(tǒng)這兩個(gè)領(lǐng)域的增長(zhǎng),，自創(chuàng)生理論在近年來(lái)受到了普遍的關(guān)注。人們還就自創(chuàng)生理論與 Prigogine的耗散結(jié)構(gòu)論進(jìn)行了比較,。Varela還曾經(jīng)研究過(guò)免疫系統(tǒng),，免疫系統(tǒng)可以被認(rèn)為是組織閉合的但卻不是自創(chuàng)生的系統(tǒng)。由于這個(gè)問(wèn)題比較 專業(yè),，我們?cè)谶@里就不討論了,。

2.4.1 最小的細(xì)胞以及生命的起源
    關(guān)于地球上的生命起源研究有兩個(gè)方法主線。第一種方法是基于酶和基因的,，它認(rèn)為生命是用分子的特征以及基因的功能和結(jié)構(gòu)來(lái)刻畫的,。第二種方法是認(rèn)為生命是 用細(xì)胞的新陳代謝特征來(lái)刻畫的。然而,，這兩種方法都沒(méi)有提供一個(gè)標(biāo)準(zhǔn)的生命模型能夠解決所有的重要問(wèn)題,。尤其是在什么樣的條件下原生化學(xué)系統(tǒng)能夠形成獲得 生命系統(tǒng)呢？我們?nèi)绾握J(rèn)識(shí)非陸地生命系統(tǒng)呢,？它們從結(jié)構(gòu)上究竟與我們有什么區(qū)別,？
    Fleischaker提出自創(chuàng)生以及最小細(xì)胞的概念一起可以給第二種方法提供一個(gè)健全的理論框架。自創(chuàng)生理論的目標(biāo)自然是給生命提供了一個(gè)有用的可操作 的定義,，雖然Fleischaker爭(zhēng)論說(shuō)自創(chuàng)生系統(tǒng)的定義需要做一定修改,。這種修改就是要把“生命”系統(tǒng)局限在物理的自創(chuàng)生系統(tǒng)而不是非物理的可能的生 命系統(tǒng)。關(guān)于這個(gè)問(wèn)題我們將在第3.3.2節(jié)討論,。
    當(dāng)我們把自創(chuàng)生理論作為生命的定義的時(shí)候,，下一個(gè)步驟就是考慮如何構(gòu)造一個(gè)基本的自創(chuàng)生的系統(tǒng)。注意,，自創(chuàng)生理論既提供了所有的東西也等于什么都沒(méi)說(shuō),。一 個(gè)自我構(gòu)建的系統(tǒng)要么存在產(chǎn)生了它自己要么根本就不存在。根本沒(méi)有兩種之間的情況,。這就導(dǎo)致了給定了地球原始的條件是否能夠涌現(xiàn)出理論上的最小細(xì)胞出來(lái),。 實(shí)際上，F(xiàn)leischaker考慮了三種不同的最小細(xì)胞的特征：最小的細(xì)胞應(yīng)該能夠代表我們熟悉的生命形式,；最小細(xì)胞應(yīng)該能夠抓住地球生命同樣也是非地 球生命的特征,。
    關(guān)于最后一點(diǎn)，沒(méi)有什么是超過(guò)應(yīng)用于物理空間自創(chuàng)生系統(tǒng)的六點(diǎn)特征的,，如果過(guò)于具體則會(huì)添加不必要的約束,。另一方面，我們可以針對(duì)現(xiàn)代的細(xì)胞詳細(xì) 論述,。這樣的細(xì)胞可以看作是“擁有DNA環(huán)狀結(jié)構(gòu),、ATP驅(qū)動(dòng)的,、具備能量轉(zhuǎn)換功能、由蛋白質(zhì)細(xì)胞膜的包裹的以酶為介質(zhì)的細(xì)胞質(zhì)溶液集體”,。這種概化的說(shuō) 明顯然可以涵蓋原核生物（如細(xì)菌）和真核生物（如海藻,、真菌、動(dòng)物,、植物細(xì)胞）甚至它們可能存在顯著不同,。

    最小的細(xì)胞途徑包含了生命的起源。第一個(gè)細(xì)胞依賴于一個(gè)非?；镜臎](méi)有后期類似酶機(jī)制的細(xì)胞,。Fleischaker建議必須能夠?qū)崿F(xiàn)一些操作：
1、細(xì)胞必須能夠展示出一個(gè)具有邊界的結(jié)構(gòu)的形成和維護(hù),。這種結(jié)構(gòu)應(yīng)該能夠創(chuàng)造出一個(gè)良好的內(nèi)部環(huán)境,，并且還能夠有選擇的輸入和輸出分子和金屬離子。現(xiàn)代 細(xì)胞研究中發(fā)現(xiàn)的磷質(zhì)雙層結(jié)構(gòu)促成了一個(gè)封閉球的形成并且避免了與水的接觸,。磷質(zhì)雙層結(jié)構(gòu)在某方面說(shuō)也是可滲透的并且可以在沒(méi)有復(fù)雜酶相互作用的條件下進(jìn) 行,，例如，它可以滲透鈉原子以及質(zhì)子,。
2、細(xì)胞還必須擁有某種保持活動(dòng)能量轉(zhuǎn)換結(jié)構(gòu)來(lái)維持自身避免化學(xué)的均衡,。一個(gè)最早的形式就是被光驅(qū)動(dòng)的光合系統(tǒng),。色素分子將會(huì)作為質(zhì)子泵潛入到細(xì)胞膜中去并引起細(xì)胞內(nèi)新材質(zhì)的集中。
3,、細(xì)胞必須使用,、轉(zhuǎn)換它自己的材料來(lái)構(gòu)建它需要的組件及邊界。這個(gè)過(guò)程的一個(gè)可能開(kāi)始是二氧化碳的輸入以及碳和氧在光的作用下的轉(zhuǎn)換,。

    最重要的不是形成這些基本操作的特定機(jī)制,，而是所有的這些操作都需要成為一個(gè)連續(xù)的動(dòng)態(tài)的自我生產(chǎn)的網(wǎng)絡(luò)整體。

2.4.2 化學(xué)自創(chuàng)生
    除了理論上的最小細(xì)胞構(gòu)建以外,，如何根據(jù)自創(chuàng)生理論以及生命的標(biāo)準(zhǔn)來(lái)判斷或者構(gòu)建一個(gè)化學(xué)系統(tǒng)也是很有趣的,。這里我們舉三個(gè)例子：自催化過(guò)程，滲透性生長(zhǎng)以及自復(fù)制膠體,。
2.4.2.1. 自催化反應(yīng)
    催化劑是一種能夠促進(jìn)化學(xué)反應(yīng)發(fā)生或者加速化學(xué)反應(yīng)的分子物質(zhì),，但并不被化學(xué)反應(yīng)本身所改變。細(xì)胞的復(fù)雜構(gòu)建（正如人們?cè)O(shè)想的生命起源的時(shí)候就存在的細(xì) 胞）需要很多的催化劑,，這恰恰是酶的一個(gè)重要功能,。一個(gè)自創(chuàng)生的過(guò)程就是一個(gè)化學(xué)反應(yīng)的副產(chǎn)品所創(chuàng)造的特定催化劑的生產(chǎn)過(guò)程。因此整個(gè)過(guò)程就是自催化的,。 一個(gè)實(shí)例是RNA分子的自構(gòu)建過(guò)程,，在特定的環(huán)境下,，RNA可以形成像酶一樣能夠與其他RNA分子反應(yīng)的復(fù)雜表面?？挤蚵?jīng)專門在復(fù)雜性理論中探討過(guò)這 些問(wèn)題,。
    雖然這個(gè)過(guò)程可以用一種自指的相互作用來(lái)表達(dá)，但是整個(gè)系統(tǒng)并不是自創(chuàng)生的,，因?yàn)樗](méi)有生產(chǎn)它自己的邊界,，因此也就不是一個(gè)能夠構(gòu)建自身的主動(dòng)的整體。 復(fù)雜的,，相互依賴的化學(xué)反應(yīng)過(guò)程雖然是普遍存在于自然界的,，但是它們并不是自創(chuàng)生的除非他們能夠形成自我約束的邊界，從而實(shí)現(xiàn)自創(chuàng)生組織,。
2.4.2.2 滲透性生長(zhǎng)
    Zeleny和Hufford建議曾經(jīng)被Leduc研究的滲透性增長(zhǎng)看作是自創(chuàng)生的,。這種生長(zhǎng)是由無(wú)機(jī)鹽的擴(kuò)展和沉淀形成的一個(gè)可滲透的邊界。氯化鈣與飽 和的鈉磷酸鹽反應(yīng)可以說(shuō)明這個(gè)過(guò)程,。鈣和磷酸鹽的交互形成了磷化鈣沉淀的細(xì)邊界層,。這個(gè)層會(huì)將磷和鈣分離，水會(huì)通過(guò)滲透穿過(guò)邊界,。提高的內(nèi)部壓力會(huì)打破沉 淀的磷化鈣,。這種穿透會(huì)進(jìn)一步促進(jìn)內(nèi)部的鈣和外部的磷接觸，因此形成進(jìn)一步的沉淀,。因此,，這個(gè)沉淀層就會(huì)進(jìn)一步增長(zhǎng)。

Zeleny和Hufford聲明這個(gè)系統(tǒng)滿足自創(chuàng)生的六個(gè)標(biāo)準(zhǔn)：
1. 首先,，滲透邊界形成了滲透性生長(zhǎng)是一個(gè)可區(qū)分的實(shí)體,；
2. 其次，它可以被分解為更小的部件例如磷化鈣邊界以及氯化鈣,；
3. 整個(gè)過(guò)程服從物理規(guī)則,；
4. 由于近鄰偏好的關(guān)系，部件磷化鈣聚集形成了邊界,；
5. 邊界是由內(nèi)部和外部部件在膜的邊界處相互作用而形成的,；
6. 組件（氯化鈣）雖然不是被細(xì)胞產(chǎn)生但是其他部件（沉淀物）生產(chǎn)的永久組成物。

    這種假設(shè)的確會(huì)引起一些問(wèn)題,，正如Leduc的系統(tǒng)明顯是無(wú)機(jī)的并且不能被稱為活的,。如果我們接受該系統(tǒng)符合現(xiàn)在的自創(chuàng)生系統(tǒng)的標(biāo)準(zhǔn)，那么我們也就會(huì)不得 不擴(kuò)展我們對(duì)生命的理解,。事實(shí)上,，滲透性生長(zhǎng)過(guò)程是否滿足那六條標(biāo)準(zhǔn)是值得爭(zhēng)議的。前三條是當(dāng)然滿足的,，但是第四條并不滿足,，因?yàn)樗⒉皇且粋€(gè)相互作用的 網(wǎng)絡(luò)在不斷生產(chǎn),。
    對(duì)于第四條，由沉淀形成的邊界并不像細(xì)胞膜,。它是一個(gè)靜態(tài)的被動(dòng)的邊界,，更像是石頭墻而不是細(xì)胞膜。它并沒(méi)有形成“近鄰偏好的相互作用”,；事實(shí)上,，這種邊 界一旦形成，它就根本沒(méi)有相互作用了,。第五條：邊界組件是由內(nèi)部生產(chǎn)過(guò)程持續(xù)不斷地生成這點(diǎn)也不滿足,，而是由邊界的破裂以及破裂處的進(jìn)一步沉淀形成的。最 后,，氯化物也不是系統(tǒng)自己生成的而是一開(kāi)始就存在的一個(gè)單一部件,。
2.4.2.3 自復(fù)制膠化物
    另外一個(gè)現(xiàn)象是Bachmann及其同志們研究的。一個(gè)膠化物就是一個(gè)有機(jī)化學(xué)物的小液滴,，如酒精滴在水中,，并且被表面活性劑包圍。反膠化物是水滴在有機(jī) 溶劑中形成的,。膠化物中會(huì)發(fā)生化學(xué)反應(yīng),，不斷產(chǎn)生更多的表面活性物。最后,，這就會(huì)導(dǎo)致膠化物的分離并形成一個(gè)新的膠化物,。整個(gè)過(guò)程是自復(fù)制的。普通膠化物 和反膠化物以及在酶催化作用下的化學(xué)反應(yīng)已經(jīng)被實(shí)驗(yàn)證實(shí),。

    在反膠化物實(shí)驗(yàn)中，水滴包含了溶解的氫氧化鋁,，表面活化劑是辛酸鈉以及1-辛醇（也是一種溶液）,。另外還有異辛烷溶液。主要的化學(xué)反應(yīng)是邊界組件不斷的產(chǎn) 生邊界組件自己,。當(dāng)鋰作催化劑的時(shí)候Octyl octanoate是可水解的,。由于氫氧化鋁在有機(jī)溶液中是不可溶解的，因此它會(huì)包在水的膠化物之中,，大量的膠化物會(huì)生成,，雖然它的尺寸會(huì)慢慢減小。
    這些系統(tǒng)被稱為是自創(chuàng)生的是值得懷疑的,。首先,，原始材料（水和鋁的混合物或者酶催化劑）不是在系統(tǒng)內(nèi)部產(chǎn)生的。這就限制了復(fù)制的發(fā)生次數(shù),，系統(tǒng)最終會(huì)停止 下來(lái),。甚至如果這些材料可以被持續(xù)添加,，系統(tǒng)仍然不是自生產(chǎn)的。第二,，單層次表面活性劑不能被原始材料輸送到膠體中,。所以，一種如真實(shí)細(xì)胞膜的雙層次邊界 就是必需的了,。進(jìn)一步,，研究者們更加關(guān)注的是膠化物的自我復(fù)制，并認(rèn)為這就是自創(chuàng)生的,。然而,，自復(fù)制是自創(chuàng)生的第二階段。無(wú)論如何,，這種現(xiàn)象說(shuō)明這不是自 創(chuàng)生的過(guò)程,。

英文原文：

2.1 The essential idea of Autopoiesis

The fundamental question Maturana and Varela set out to answer is: what distinguishes entities or systems that we would call living from other systems, apparently equally complex, which we would not? How, for example, should a Martian distinguish between a horse and a car? This is an example that Monod (1974, p. 19) uses in addressing the similar but not identical question of distinguishing between natural and artificial systems.

This has always been a problem for biologists, who have developed a variety of answers. First came vitalism (Bergson, 1911; Driesch, 1908), which held that there is some substance or force or principle, as yet unobserved, which must account for the peculiar characteristics of life. Then system theory, with the development of concepts such as feedback, homeostasis, and open systems, paved the way for explanations of the complex, goal-seeking behavior of organisms in purely mechanistic term ( for example, Cannon, 1939; Priban, 1968). While this was a significant advance, such mechanisms could equally well be built into simple machines that would never qualify as living organisms.

A third approach, the most common recently, is to specify a list of necessary characteristics that any living organism must have – such as reproductive ability, information-processing capabilities, carbon-based chemistry, and nucleic acids (see, for example, Miller, 1978; Bunge, 1979). The first difficulty with this approach is that it is entirely descriptive and not in any real sense explanatory. It works by observing systems that are accepted as living and noting some of their common characteristics. However, this tactic assumes precisely that which is in need of explanation – the distinction between the living and the nonliving. The approach fails to define the characteristics particular to living systems alone or to give any explanation as to how such characteristics might generate the observed phenomena. Second, there is, inevitably, always a lack of agreement about the contents of such lists. Any two lists will contain different characteristics, and it is difficult to prove that every feature in a list is really necessary or that the list is actually complete.

Maturana’s and Varela’s work is based on a number of fundamental observations about the nature of living systems. They will be introduced briefly here but discussed in more detail in later chapters.

1. Somewhat in opposition to current trends that focus on the species or the genes (Dawkins,1978), Maturana and Varela pick out the single, biological individual (for instance, a single celled creature such as an amoeba) as the central example of a living system. One essential feature of such living entities is their individual autonomy. Although they are part of organisms, populations, and species and are affected by their environment, individuals are bounded, self-defined entities.

2. Living systems operate in an essentially mechanistic way. They consist of particular components that have various properties and interactions. The overall behavior of the whole is generated purely by these components and their properties through the interactions of neighboring elements. Thus any explanation of living systems must be a purely mechanistic one.

3. All explanations or descriptions are made by observers (i.e., people) who are external to the system. One must not confuse that which pertains to the observer with that which pertains to the observed. Observers can perceive both an entity and its environment and see how the two relate to each other. Components within an entity, however, cannot do this, but act purely in response to other components.

4. The last two lead to the idea that any explanation of living systems should be nonteleological, i.e., it should not have recourse to ideas of function and purpose. The observable phenomena of living systems result purely from the interactions of neighboring internal components. The observation that certain parts appear to have a function with regard to the whole can be made only by an observer who can interact with both the component and with the whole and describe the relation of the two.

To explain the nature of living systems, Maturana and Varela focus on a single basic example – the individual, living cell. Briefly, a cell consists of cell membrane or boundary enclosing various structures such as nucleus, mitochondria, and lysosomes as well as many (and often complex) molecules produced from within. These structures are in constant chemical interplay both with each other and, in the case of the membrane, with their external medium. It is a dynamic, integrated chemical network of incredible sophistication (see for example Alberts et al.,1989; Raven and Johnson,1991).

What is it that characterizes this as an autonomous, dynamic, living whole? What distinguishes it from machine such as a chemical factory which also consists of complex components and interacting processes of production forming an organized whole? It can not be to do with any functions or purposes that any single cell might fulfill in a larger multi-cellular organism since there are single-cellular organisms that survive by themselves. Nor can it explained in a reductionist way through particular structures or components of the cell such as the nucleus or DNA/RNA. The difference must stem from the way of the parts are organized as a whole. To understand Maturana and Varela’s answer, we need to look at two related questions – what is it that the cell does, that is what is it the cell produces? And what is it that produces the cell? By this I mean the cell itself rather than the results of their reproduction.

What does a cell do? This will be looked at in detail in Section 2.3 but, in essence, it produces many complex and simple substances which remain in the cell (become of the cell membrane) and participate in those very same production processes. Some molecules are excreted from the cell, through the membrane, as waste. What is it that produces the components of the cell? With the help of some basic chemicals imported from its medium, the cell produces its own constituents. So a cell produces its own components, which are therefore what produces it in a circular, ongoing process (Fig. 2.1)

It produces, and is produced by, nothing other than itself. This simple idea is all that is meant by autopoiesis. The word means “self-producing” and that is what the cell does: it continually produces itself. Living systems are autopoietic – they are organized in such a way that their processes produce the very components necessary for the continuance of these processes. Systems which do not produce themselves are called allopoietic, meaning “other-producing” – for example, a river or a crystal. Maturana and Varela also refer to human-created systems as heteropoietic. An exemple is a chemical factory. Superficially, this is similar to cell, but it produces chemicals that are used elsewhere, and is itself produced or maintained by other systems. It is not self-producing.

At first sight this may seem an almost trivial idea, yet further contemplation reviews how significance it is. For example:
1. Imagine try to build autopoietic machine. Save for energy and some basic chemicals, everything within it would itself have to be produced by the machine itself. So, there would have to be machines to produce the various components. Of course, these machines themselves would have to be produced, maintained, and repaired by yet more machines, and so on, all within the same single entity. The machine would soon encompass the whole economy.
2. Suppose that you succeed. Then surely what you have created would be autonomous and independent. It would have the ability to construct and reconstruct itself, and would, in a very real sense, be no longer controlled by us, its creators. Would it not seem appropriate to call it living?
3. As life on earth originated from a sea of chemicals, a cell in which a set of chemicals interacted such that the cell created and re-created its own constituents would generate a stable, self-defined entity with a vastly enhanced chance of future development. This indeed is the basis for current research, to be described in section 2.4.1
4. What of death? If, for some reason, either internal or external, any part of the self-production process breaks down, then there is nothing else to produce the necessary components and the whole process falls apart. Autopoiesis is all or nothing – all the processes must be working, or the systems disintegrates.

This, then, is the central idea of autopoiesis: a living system is one organized in such a way that all its components and processes jointly produce those self-producing entity. This concept has nearly been grasped by other biologists, as the quotation from Rose at the start of this chapter shows. But Maturana and Varela were the first to coin a word for this life-generating mechanism, to set out criteria for it (Varela et al., 1974), and to explore its consequences in a rigorous way.

Considering the derivation of the word itself, Maturana explains that he had the main idea of a circular, self-referring organization without the term autopoiesis. In fact, biology of cognition, the first major exposition of the idea, does not use it. Maturana coined the term in relation to the distinction between praxis (the path of arms, or action) and poiesis (the path of letters, or creation). However, it is interesting to see how closely Maturana’s usage of auto- and allopoiesis is actually foreshadowed by the German phenomenological philosopher Martin Heidegger. In the quotation at the start of Chapter 1, Heidegger uses the term poiesis as a bringing-forth and draws the contrast between the self-production (heautoi) of nature and the other-production (alloi) that humans do. Heidegger’s relevance to Maturana’s work will be considered further in Section 7.5.2

2.2 Formal Specification of Autopoiesis
Now that I have sketched the idea in general terms, this section will describe in more detail Maturana’s and Varela’s specification and vocabulary.
We begin from the observation that all descriptions and explanations are made by observers who distinguish an entity or phenomenon from the general background. Such descriptions always depend in part on the choices and processes of the observer and may or may not correspond to the actual domain of the observed entity. That which is distinguished by an observer, Maturana calls a unity, that is, a whole distinguished from a background. In making the distinction, the properties which specify the unity as a whole are established by the observer. For example, in calling something “a car,” certain basic attributes or defining features (it is mobile, carries people, is steerable) are specified. An observer may go further and analyze a unity into components and their relations. There are different, equally valid, ways in which this can be done. The result will be a description of a composite unity of components and the organization which combines its components together into a whole.

Maturana and Varela draw an important distinction between the organization of a unity and its structure:
[Organization]refers to the relations between components that define and specify a system as a composite unity of a particular class, and determine its properties as such a unity … by specifying a domain in which it can interact as an unanalyzable whole endowed with constitutive properties.
[Structure] refers to the actual components and the actual relations that these must satisfy in their participation in the constitution of a given composite unity [and] determines the space in which it exists as a composite unity that can be perturbed through the interactions of its components, but the structure does not determine its properties as a unity.
Maturana (1978, p. 32)

The organization consists of the relations among components and the necessary properties of the components that characterize or define the unity in general as belonging to a particular type or class. This determines its properties as a whole. At its most simple, we can illustrate this distinction with the concept of a square. A square is defined in terms of the (spatial) relations between components – a figure with four equal sides, connected together at right angles. This is its organization. Any particular physically existing square is a particular structure that embodies these relations. Another example is a an airplane, which may be defined by describing necessary components such as wings, engines, controls, brakes, seating, and the relations between them allowing it to fly. If a unity has such an organization, then it may be identified as a plane since this particular organizatio would produce the properties we expect in a plane as a whole. Structure, on the other hand, describes the actual components and actual relations of a particular real example of any such entity, such as the Boeing 757 I board at the airport.

This is a rather unusual use of the term structure (Andrew, 1979). Generally, in the description of a system, structure is contrasted with process to refer to those parts of the system which change only slowly; structure and organization would be almost interchangeable. Here, however, structure refers to both the static and dynamic elements. The distinction between structure and organization is between the reality of an actual example and the abstract generality lying behind all such examples. This is strongly reminiscent of the philosophy of classic structuralism in which an empirical surface “structure” of events is related to an unobservable deep structure (“organization”) of basic relationships which generate the surface.

An existing, composite unity, therefore, has both a structure and an organization. There are many different structures that can realize the same organization, and the structure will have many properties and relations not specified by the organization and essentially irrelevant to it – for example, the shape, color, size, and material of a particular airplane. Moreover, the structure can change or be changed without necessarily altering the organization. For example, as the plane ages, has new parts installed, and gets repainted it still maintains its identity as a plane because its underlying organization has not changed. Some changes, however, will not be compatible with the maintenance of the organization – for example, a crash which converts the plane into a wreck.

The essential distinction between organization and structure is between a whole and its parts. Only the plane as a whole can fly – this is its constitutive property as a unity, its organization. Its parts, however, can interact in their own domains depending on all their properties, but they do so only as individual components. Sucking in a bird can stop an engine; a short circuit can damage the controls. These are perturbations of the structure, which may affect the whole and lead to a loss of organization or which may be compensable, in which can the plane is still able to fly.

With this background, we can consider Maturana’s and Varela’s definition of autopoiesis. A unity is characterized by describing the organization that defines the unity as a member of a particular class that is, which can be seen to generate the observed behavior of unities of that type. Maturana and Varela see living systems as being essentially characterized as dynamic and autonomous and hold that it is their self-production which leads to these qualities. Thus the organization of living systems is one of self-production – autopoiesis. Such an organization can, of course, be realized in infinitely many structures.

A more explicit definition of an autopoietic system is
A dynamic system that is defined as a composite unity as a network of productions of components that,
a) through their interactions recursively regenerate the network of productions that produced them, and
b) realize this network as a unity in the space in which they exist by constituting and specifying its boundaries as surfaces of cleavage from the background through their preferential interactions within the network, is an autopoietic system. Maturana (1980b, p. 29)

The first part of this quotation details the general idea of a system of self-production, while the second specifies that the system must be actually realized in an entity that produces its own boundaries. This latter point, about producing boundaries, is particularly important when one attempts to apply autopoiesis to other domains, such as the social world, and is a recurring point of debate. Notice also that the definition does not specify that the realization must be a physical one, although in the case of a cell it clearly is. This leaves open the idea of some abstract autopoietic systems such as a set of concepts, a cellular automaton, or a process of communication. What might the boundaries of such a system be? And would we really want to call such a system “living”? Again, this is the subject of much debate – See section 3.3.2

This somewhat bare concept is further developed by considering the nature of such an organization. In particular, as an organization it will involve particular relations among components. These relations, in the case of a physical system, must be of three types according to Maturana and Varela (1973): constitution, specification, and order. Relations of constitution concern the physical topology of the system (say, a cell) – its three-dimensional geometry. For example, that it has a cell membrane, that components are particular distances from each other, that they are the required sizes and shapes. Relations of specification determine that the components produced by the various production processes are in fact the specific ones necessary for the continuation of autopoiesis. Finally, relations of order concern the dynamics of the processes – for example, that the appropriate amounts of various molecules are produced at the correct rate and at the correct time. Specific examples of these relations will be given later, but it can be seen that these correspond roughly to specifying the “where”,”what”, and “when” of the complex production processes occurring in the cell.

It might appear that this description of relations “necessary” for autopoiesis has a functionalist, teleological tone. This is not really the case, as Maturana and Varela strongly object to such explanations. It is simply that, if such components and relationships do occur, they give rise to electrochemical processes that themselves produce further components and processes of the right types and at the right rates to generate an autopoietic system. But there is no necessity to this; it is simply a combination that does, or does not, occur, just as a plant may, or may not, grow depending on the combination of water, light, and nutrients.

In an early attempt to make this abstract characterization more operational, a computer model of an autopoietic cellular automaton was developed together with a six-point key for identifying an autopoitic system (Varela et al., 1974). The key is specified as follows:

i) Determine, through interactions, if the unity has identifiable boundaries. If the boundaries can be determined, proceed to 2. If not, the entity is indescribable and we can say nothing.
ii) Determine if ther are constitutive elements of the unity, that is, components of the unity. If these components can be described, proceed to 3. If not, the unity is an unanalyzable whole and therefore not an autopoietic system.
iii) Determine if the unity is a mechanistic system, that is, the component properties are capable of satisfying certain relations that determine in the unity the interactions and transformations of these components. If this is the case, proceed to 4. If not, the unity is not an autopoietic system.
iv) Determine if the components that constitute the boundaries of the unity constitute these boundaries through preferential neighborhood interactions and relations between themselves, as determined by their properties in the space of their interactions. If this is not the case, you do not have an autopoietic unity because you are determining its boundaries, not the unity itself. If 4 is the case, however, proceed to 5.
v) Determine if the components of the boundaries of the unity are produced by the interactions of the components of the unity, either by transformation of previously produced components, or by transformations and/or coupling of non-component elements that enter the unity trough its boundaries. If not, you do not have an autopoietic unity; if yes proceed to 6.
vi) If all the other components of the unity are also produced by the interactions of its components as in 5, and if those which are not produced by the interactions of other components participate as necessary permanent constitutive components in the production of other components, you have an autopoietic unity in the space in which its components exist. If this is not the case, and there are components in the unity not produced by components of the unity as in 5, or if there are components of the unity which do not participate in the production of other components, you do not have an autopoietic unity.

The first three criteria are general, specifying that there is an identifiable entity with a clear boundary, that it can be analyzed into components, and that it operates mechanistically, i.e., its operation is determined by the properties and relations of its components. The core autopoietic ideas are specified in the last three points. These describe a dynamic network of interacting processes of production (vi), contained within and producing a boundary (v) that is maintained by the preferential interactions of components. The key notions, especially when considering the extension of autopoiesis to nonphysical systems, are the idea of production of components, and the necessity for a boundary constituted by produced components.

These key criteria will be applied to the cell in the next section. This section will describe briefly embodiments of the autopoietic relations outlined above in the chemistry of the cell. Alberts et al. or Freifelder are good introductions to molecular biology, as is Raven and Johnson to the cell.

2.3 An illustration of Autopoiesis in the Cell
This section will describe briefly embodiments of the autopoietic relations outlined above in the chemistry of the cell. Alberts et al. are good introductions to molecular biology, as is Raven and Johnson to the cell.
2.3.1 Applying the Six Criteria
Zeleny and Hufford analyze a typical cell with the six key points. A schematic of two typical cells is shown in Fig 2. One is a eukaryotic cell, i.e., one that has a nucleus, and the other is a prokaryotic cell, which does not.
1. The cell has an identifiable boundary formed by the plasma membrane. Thus, the cell is identifiable.
2.The cell has identifiable components such as the mitochondria, the nucleus, and the membranous network known as the endoplasmic reticulum. Thus, the cell is analyzable.
3. The components have electrochemical properties that follow general physical laws determining the transformations and interactions that occur within the cell. Thus, the cell is a mechanistic system.
4.The boundary of the cell is formed by a plasma membrane consisting of phospholipids molecules and certain proteins (fig 3). The lipid molecules are aligned in a double layer, forming a selectively permeable barrier; the proteins are wedged in this bilayer, mediating many of the membrane functions. A lipid molecule consists of two parts – a polar head, which is attracted to water, and a hydrocarbon (fatty) tail, which is repelled. In solution, the tails join together to form the two layers with the heads outside. The integral proteins also have areas that seek or avoid water. The boundary is therefore self-maintained through preferential neighborhood relations.
5. The lipid and protein components of the boundary are themselves produced by the cell. For example, most of the lipid molecules required for new membrane formation are produced by the endoplasmic reticulum, which is itself a complex, membranous component of the cell. The boundary components are thus self-produced.
6. All of the other components of the cell (e.g., the mitochondria, the nucleus, the ribosomes, the endoplasimic reticulum) are also produced by and within the cell. Certain chemicals (such as metal ions) not produced by the cell are imported through the membrane and then become part of the operations of the cell. Cell components are thus self-produced.

2.3.2 Autopoietic Relations of Constitution, Specification, and Order
Apart from the six-point key, autopoiesis was also defined by three necessary types of relations. These can be illustrated as follows for a typical cell.
2.3.2.1 Relations of Constitution
Relations of constitution determine the three-dimensional shape and structure of the cell so as to enable the other relations of production to be maintained. This occurs through the production of molecules which, through their particular stereochemical properties, enable other processes to continue.
An obvious example is the construction of membranes or cell boundaries. In animal cells, the membrane surrounding the mitochondria, like that around the cell itself, serves to harbor cell contents and control the rate of reaction through diffusion. Various reactive molecules are distributed along the inner membrane in an appropriate order to allow energy-producing sequences to proceed efficiently. In plant cells, in addition to the plasma membrane, there is a cell wall, which consists of cellulose, a material made up of long, straight chains of glucose units packed together to form strong rigid threads. These give plants their rigidity.
A second example is the active sites on enzymatic proteins. These act as catalysts for most reactions, changing a particular substrate in an appropriate way to allow it to react more easily. Generally, the active site is found in certain specific parts of the enzyme molecule where the configuration of amino acids is structured to fit the particular substrate, sometimes with the help of “activators” or co-enzymes. The substrate molecule interlocks with the active site and in so doing changes appropriately so that it no longer fits, and thus frees itself.
2.3.2.2 Relations of Specification
These determine the identity, in chemical properties, of the components of the cell in such a way that through their interactions they participate in the production of the cell. There are two main types of structural correspondence, that among DNA, RNA, and the proteins they produce and that between enzymes and the substrates they catalyze.
Protein synthesis is particularly complex because each protein is formed by linking up to twenty different amino acids in a specific combination, often containing 300 or more units in all. This requires an RNA template molecule, tailor-made for each protein, containing specific spaces for each of the amino acids in order, together with an enzyme and t-RNA for each acid.

As already mentioned, enzymes are necessary to help most of the reactions in the cell, and again, each specific reaction requires an enzyme specific to the reaction and to the substrate involved. Hundreds of such enzymes are needed, and all must be produced by the cell.

2.3.2.3 Relations of Order
Relations of order concern the dynamics of the cell’s production processes. Various chemicals and complex feedback loops ensure that both the rate and the sequence of the various production processes continue autopoiesis. For instance, the production of energy through oxidation is controlled by the amount of phosphate and ADP (adenosine diphosphate) in the mitochondria. At the same time, reactions that use energy actually produce ADP and phosphate so that, automatically, a high usage of energy leads to a high production rate of these necessary substances.

2.3.3 Other Possible Autopoietic Systems
An interesting question leading from the idea of the cell as an autopoietic system is whether or not there are other instances of autopoietic systems. Are multicellular organisms also autopoietic systems? Maturana is equivocal, suggesting that organisms such as animals and plants may be second-order autopoietic systems, with the components being not the cells themselves but various molecules produced by the cells. On the other hand, he suggests that some cellular systems may not actually constitute autopoietic systems, but may be merely colonies. What about a system that appears to have a closed and circular organization but is not generally classified as living, such as the pilot light of a gas boiler? Finally, what about nonphysical systems such as the autopoietic automata mentioned in section 2.2.1 and described more fully in section 4.4, or systems such as a set of ideas or a society? These possibilities will be discussed in more detail in Section 3.3.

2.4．Applications of Autopoiesis in Biology and Chemistry
One would have expected that, given the importance and nature of its claims, autopoiesis would have had a major impact on the field of biology. In fact, for many years there was a noticeable reluctance to take the ideas seriously at all. In 1979, I wrote to an eminent British biologist – Professor Steven Rose at the Open University – querying the status of autopoiesis. He replied to the effect that he did not wish to comment on autopoiesis but that Maturana was a reputable biologist. One notable exception is Lynn Margulis, whose own theory, that eukaryotic cells evolved through the symbiosis of simpler units, is itself quite controversial.

However, recently interest has been growing in two areas: research into the origins of life and the creation of chemical systems that, although not living, display some of the characteristics of autopoietic self-production. Autopoiesis has also been compared with Prigogine’s dissipative structures. Varela has also pursued work on the nature of the immune system, viewing it as organizationally closed but not autopoietic. However, as this topic is very technical and not of primary relevance, it cannot be pursued here.

2.4.1 Minimal Cells and the Origin of Life
There are two main lines of approach to theories concerning the origin of life on Earth. In the first approach, based on study of the enzymes and genes, life is characterized as being molecular and a defining feature is the structure and function of the genes. In the second approach, life is characterized as cellular, and its defining feature is metabolic functioning within the cell. However, neither approach can really specify a standard or model for life against which important questions may be answered. In particular, at what point did prebiotic chemical systems become biotic living systems? And how could we recognize nonterrestrial living systems. Which might be radically different in structure from our own?
Fleischaker proposes that the concept of autopoiesis, together with notions of minimal cell, can provide a sound theoretical framework to tackle these questions within the second tradition mentioned above. Autopoiesis clearly does aim to provide a specific and operationally useful definition of life, although Fleischaker argues that the concept of autopoiesis does need some modification. This modification would restrict “living” systems to autopoietic system in the physical domain rather that allow the possibility of nonphysical living systems, a possibility which ( as mentioned above) is left open by the formal definition of autopoiesis. This will be discussed in Section 3.3.2

Given autopoiesis (or modified version) as a definition of life, the next step in theorizing about the origin of life is to consider how an elementary autopoietic system might have formed. Note that autopoiesis is all or nothing. A self-producing system either exists and produces itself or it does not – there can be no halfway stage. This leads to the idea of a theoretical “minimal” cell which could plausibly emerge, given the early conditions on earth. In fact, Fleischaker considers three different characterizations of minimal cells: a minimal cell representative of the evolved life forms that we know today; a minimal cell that would characterize both terrestrial and nonterrestrial life regardless of its constituents.

About the last, little can be put forward beyond the six-point autopoietic characteristics in the physical space; to be more specific would constrain the possibilities unnecessarily. On the other hand, we can be quite specific about a modern-day cell. Such a cell could be described as “a volume of cytoplasmic solvent capable of DNA-cycled, ATP-driven and enzyme-mediated metabolism enclosed within a phosphor-lipoprotein membrane capable of energy transduction”, This generalized specification can cover both prokaryotes (bacterial) and eukaryotes (algal, fungal, animal, and plant cells) even though there are important differences in their operation.

The most interesting minimal cell scenario concerns the origin of life. The first cell need be only a very basic cell without the later elaborations such as enzymes. Fleischaker suggests that such a cell must exhibit a number of operations (Fig.2.4):
1、The cell must demonstrate the formation and maintenance of a boundary structure that creates a hospitable inner environment and allows selective permeability for incoming and outgoing molecules and ions. The lipid bilayer found in contemporary cells is a good possibility since the hydropholic nature of lipid molecules leads them to form closed spheres in order to avoid contact with water. Lipid bilayers are also permeable in certain ways – for example, to flows of protons or sodium atoms – without the need for the complex enzymes prevalent in contemporary cells.
2. The cell must also demonstrate some form of active energy transduction to maintain it away from entropic chemical equilibrium. One possibility is an early form of photopigment system driven by light. Pigment molecules would become embedded in the membrane and act as proton pumps, leading to the concentration of variety of raw material in the cell.
3. The cell would also need to transport and transform material elements and use these in the production of the cell’s components and its boundary. A possible start in this direction would be the import of carbon dioxide and the physio-chemical transformation of its carbon and oxygen through light-driven carbon fixation.

What is important is not the particular mechanisms for any of these general operations but that whichever mechanisms are postulated, all operations need to be part of a continuous network to form a dynamic, self-producing whole.

2.4.2 Chemical Autopoiesis
Beyond theoretical constructs of minimal cells, it is also interesting to look at attempts to identify or create chemical systems based on autopoietic criteria, and to consider whether or not these are living. We shall look at three examples: autocatalytic processes, osmotic growth, and self-replicating micelles.
2.4.2.1. Autocatalytic Reactions
A catalyst is a molecular substance whose presence is necessary for the occurrence of a particular chemical reaction, or which speeds the reaction up, but which is not changed by the reaction. The complex productions of contemporary cells (as opposed to cells that may have existed at the origin of life) require many catalysts, and this is one of the main functions of the enzymes. An autocatalytic process is one in which the specific catalysts required are themselves produced as by-products of the reactions. The process thus self-catalyzes. An example is RNA itself which, in certain circumstances, can form a complex surface that acts like an enzyme in reaction with other RNA molecules (Alberts et al.) Kauffman has a detailed discussion within the context of complexity theory.

Although this process can be described as a self-referring interaction, the system does not qualify as autopoietic because it does not produce its own boundary components and thus cannot establish itself as an autonomous operational entity (Maturana and Varela). Complex, interdependent chemical processes abound in nature, but they are not autopoietic unless they form self-bounded unities that embody the autopoietic organization.

2.4.2.2 Osmotic Growth
Zeleny and Hufford have suggested that a particular form of osmotic growth, studied by Leduc, can be seen as autopoietic. The growth is precipitation of inorganic salt that expands and forms a permeable osmotic boundary. This can be demonstrated by putting calcium chloride into a saturated solution of sodium phosphate. Interaction of the calcium and phosphate ions leads to the precipitation of calcium phosphate in a thin boundary layer. This layer then separates the phosphate from the calcium, water enters through the boundary by osmosis, and the increased internal pressure breaks the precipitated calcium phosphate. This break allows further contact between the internal calcium and the external phosphate, leading to further precipitation. Thus the precipitated layer grows.
Zeleny and Hufford argue that this system fulfills the six autopoietic criteria:
1. It is distinguishable entity because of its precipitate boundary.
2. It is analyzable into components such as the calcium phosphate boundary and the calcium chloride.
3. It follows mechanistic laws.
4. The boundary components (calcium phosphate) aggregate because of their preferred neighborhood relations.
5. The boundary components are formed by the interaction of internal and external components following osmosis through the membrane.
6. The components (calcium chloride) are not produced by the cell but are permanent constituent components in the production of other components (the precipitate)

This hypothesis does cause problems, as Leduc’s system is clearly inorganic and not what would be called living. If it is accepted that the system does properly fulfill the criteria of autopoiesis, i.e., that it is an autopoietic system as currently defined, then either we must expand our concept of living or accept that autopoiesis is in need of redefinition to exclude such examples. In fact, it is debatable whether or not this osmotic growth does correctly fulfill the six criteria. It certainly meets the first three, but it is not clear that it is a dynamic network of processes of production.

As for the fourth criterion, the precipitate that forms the boundary is unlike a cell membrane. It is static and inactive, more like a stone wall than an active membrane. It is not formed through “preferential neighborhood interactions”; in fact, once formed, it does not interact at all. Considering the fifth criterion, the boundary components are not continuously produced by the internal processes of production. Rather, a split or rupture occurs and more boundary is precipitated at the split through the interaction of internal and external chemicals. It is only because of, and at, the rupture that new boundary is produced. Finally, chloride, which is introduced artificially at the beginning, is not produced by the system, and eventually runs out.

2.4.2.3 Self-replicating Micelles
An approach with more potential, currently being researched by Bachmann and colleagues, was first proposed by Luisi. It has been discussed by Maddox and Hadlington. A micelle is a small droplet of an organic chemical such as alcohol stabilized in an aqueous solution by a boundary or “surfactant” A reverse micelle is a droplet of water similarly stabilized in an organic solvent. Chemical reactions occur within the micelle, producing more of the boundary surfactant. Eventually, this leads to the splitting of the micelle and the generation of a new one, a process of self-replication. Experiments have been carried out with both ordinary and reverse micelles and with an enzymatically driven system.

In the reverse micelle experiments, the water droplets contain dissolved lithium hydroxide, one of the surfactants is sodium octanoate, and the other is 1-octanol, which is also a solvent. The other solvent is isooctane. The main reaction is one in which the components of the boundary are themselves produced at the boundary. Octyl octanoate is hydrolyzed using the lithium as a catalyst. This produces both the surfactants (sodium octanoate and 1-octanol). Since the lithium hydroxide is insoluble in the organic solvent, it remains within the water micelle, thus confining the reaction to the boundary layer. Once the system is initiated, large numbers of new micelles are produced, although the average size of the micelles decreases.

It is not clear that these systems could yet be called autopoietic. First, the raw materials(the water-lithium mixture or the enzyme catalyst) are not produced within the system. This limits the amount of replication which can occur; the system eventually stops. Even if these materials could be added on a regular basis, the system would still not be self-producing. Second, the single-layer surfactant does not allow transport of raw materials into the micelle. For this to happen, a double-layer boundary would be necessary, as exists in actual cell membranes. Moreover, the researchers themselves, and seem most interested in the fact that the micelles reproduce themselves, and seem to identify this as autopoietic. However, reproduction of the whole is quite secondary to the autopoietic process of self-production of components. Nevertheless, this does represent an interesting step toward generating real autopoietic systems.