Chapter 2

We must now proceed to inquire into the cause why one sleeps and wakes, and into the particular nature of the sense-perception, or sense-perceptions, if there be several, on which these affections depend. Since, then, some animals possess all the modes of sense-perception, and some not all, not, for example, sight, while all possess touch and taste, except such animals as are imperfectly developed, a class of which we have already treated in our work on the soul; and since an animal when asleep is unable to exercise, in the simple sense any particular sensory¹ faculty² whatever, it follows that in the state called sleep the same affection must extend to all the special senses; because, if it attaches itself to one of them but not to another, then an animal while asleep may perceive with the latter; but this is impossible.

Now, since every sense has something peculiar³, and also something common; peculiar, as, e.g. seeing is to the sense of sight, hearing to the auditory sense, and so on with the other senses severally; while all are accompanied by a common power, in virtue⁴ whereof a person perceives that he sees or hears (for, assuredly, it is not by the special sense of sight that one sees that he sees; and it is not by mere⁵ taste, or sight, or both together that one discerns, and has the faculty of discerning, that sweet things are different from white things, but by a faculty connected in common with all the organs of sense; for there is one sensory function, and the controlling sensory faculty is one, though differing as a faculty of perception in relation to each genus of sensibles, e.g. sound or colour); and since this [common sensory activity] subsists⁶ in association chiefly with the faculty of touch (for this can exist apart from all the other organs of sense, but none of them can exist apart from it-a subject of which we have treated in our speculations⁷ concerning the Soul); it is therefore evident that waking and sleeping are an affection of this [common and controlling organ of sense-perception]. This explains why they belong to all animals, for touch [with which this common organ is chiefly connected], alone, [is common] to all [animals].

For if sleeping were caused by the special senses having each and all undergone some affection, it would be strange that these senses, for which it is neither necessary nor in a manner possible to realize their powers simultaneously⁸, should necessarily all go idle and become motionless simultaneously. For the contrary experience, viz. that they should not go to rest altogether, would have been more reasonably anticipated. But, according to the explanation just given, all is quite clear regarding those also. For, when the sense organ which controls all the others, and to which all the others are tributary⁹, has been in some way affected¹⁰, that these others should be all affected at the same time is inevitable¹¹, whereas, if one of the tributaries¹² becomes powerless, that the controlling organ should also become powerless need in no wise follow.

It is indeed evident from many considerations that sleep does not consist in the mere fact that the special senses do not function or that one does not employ them; and that it does not consist merely in an inability to exercise the sense-perceptions; for such is what happens in cases of swooning. A swoon means just such impotence of perception, and certain other cases of unconsciousness also are of this nature. Moreover, persons who have the bloodvessels in the neck compressed become insensible. But sleep supervenes when such incapacity of exercise has neither arisen in some casual organ of sense, nor from some chance cause, but when, as has been just stated, it has its seat in the primary organ with which one perceives objects in general. For when this has become powerless all the other sensory organs also must lack power to perceive; but when one of them has become powerless, it is not necessary for this also to lose its power.

We must next state the cause to which it is due, and its quality as an affection. Now, since there are several types of cause (for we assign equally the ‘final’, the ‘efficient’, the ‘material’, and the ‘formal’ as causes), in the first place, then, as we assert that Nature operates for the sake of an end, and that this end is a good; and that to every creature which is endowed by nature with the power to move, but cannot with pleasure to itself move always and continuously, rest is necessary and beneficial; and since, taught by experience, men apply to sleep this metaphorical¹³ term, calling it a ‘rest’ [from the strain of movement implied in sense-perception]: we conclude that its end is the conservation of animals. But the waking state is for an animal its highest end, since the exercise of sense-perception or of thought is the highest end for all beings to which either of these appertains; inasmuch as these are best, and the highest end is what is best: whence it follows that sleep belongs of necessity to each animal. I use the term ‘necessity’ in its conditional¹⁴ sense, meaning that if an animal is to exist and have its own proper nature, it must have certain endowments; and, if these are to belong to it, certain others likewise must belong to it [as their condition.]

The next question to be discussed is that of the kind of movement or action, taking place within their bodies, from which the affection of waking or sleeping arises in animals. Now, we must assume that the causes of this affection in all other animals are identical with, or analogous¹⁵ to, those which operate in sanguineous animals; and that the causes operating in sanguineous animals generally are identical with those operating in man. Hence we must consider the entire subject in the light of these instances [afforded by sanguineous animals, especially man]. Now, it has been definitely settled already in another work that sense-perception in animals originates ill the same part of the organism in which movement originates. This locus¹⁶ of origination is one of three determinate loci, viz. that which lies midway between the head and the abdomen¹⁷. This is sanguineous animals is the region of the heart; for all sanguineous animals have a heart; and from this it is that both motion and the controlling sense-perception originate. Now, as regards movement, it is obvious that that of breathing and of the cooling process generally takes its rise there; and it is with a view to the conservation of the [due amount of] heat in this part that nature has formed as she has both the animals which respire, and those which cool themselves by moisture. Of this [cooling process] per se we shall treat hereafter. In bloodless animals, and insects, and such as do not respire, the ‘connatural spirit’ is seen alternately puffed¹⁸ up and subsiding¹⁹ in the part which is in them analogous [to the region of the heart in sanguineous animals]. This is clearly observable in the holoptera [insects with undivided wings] as wasps²⁰ and bees; also in flies and such creatures. And since to move anything, or do anything, is impossible without strength, and holding the breath produces strength-in creatures which inhale²¹, the holding of that breath which comes from without, but, in creatures which do not respire, of that which is connatural (which explains why winged insects of the class holoptera, when they move, are perceived to make a humming noise, due to the friction²² of the connatural spirit colliding with the diaphragm); and since movement is, in every animal, attended with some sense-perception, either internal or external, in the primary organ of sense, [we conclude] accordingly that if sleeping and waking are affections of this organ, the place in which, or the organ in which, sleep and waking originate, is self-evident [being that in which movement and sense-perception originate, viz. the heart].

Some persons move in their sleep, and perform many acts like waking acts, but not without a phantasm or an exercise of sense-perception; for a dream is in a certain way a sense-impression. But of them we have to speak later on. Why it is that persons when aroused remember their dreams, but do not remember these acts which are like waking acts, has been already explained in the work ‘Of Problems’.

1 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

2 faculty   

n.才能；学院，系；(学院或系的)全体教学人员

参考例句：

• He has a great faculty for learning foreign languages.他有学习外语的天赋。
• He has the faculty of saying the right thing at the right time.他有在恰当的时候说恰当的话的才智。

3 peculiar   

adj.古怪的，异常的；特殊的，特有的

参考例句：

• He walks in a peculiar fashion.他走路的样子很奇特。
• He looked at me with a very peculiar expression.他用一种很奇怪的表情看着我。

4 virtue   

n.德行，美德；贞操；优点；功效，效力

参考例句：

• He was considered to be a paragon of virtue.他被认为是品德尽善尽美的典范。
• You need to decorate your mind with virtue.你应该用德行美化心灵。

5 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

6 subsists   

v.（靠很少的钱或食物）维持生活，生存下去( subsist的第三人称单数 )

参考例句：

• This plant subsists in water holes only during the rainy season. 这种植物只有雨季在水坑里出现。 来自辞典例句
• The hinge is that the enterprise subsists on suiting the development of data communication. 适应数据通信的发展是通信企业生存的关键。 来自互联网

7 speculations   

n.投机买卖( speculation的名词复数 )；思考；投机活动；推断

参考例句：

• Your speculations were all quite close to the truth. 你的揣测都很接近于事实。 来自《现代英汉综合大词典》
• This possibility gives rise to interesting speculations. 这种可能性引起了有趣的推测。 来自《用法词典》

8 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

9 tributary   

n.支流；纳贡国；adj.附庸的；辅助的；支流的

参考例句：

• There was a tributary road near the end of the village.村的尽头有条岔道。
• As the largest tributary of Jinsha river,Yalong river is abundant in hydropower resources.雅砻江是金沙江的最大支流，水力资源十分丰富。

10 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

11 inevitable   

adj.不可避免的，必然发生的

参考例句：

• Mary was wearing her inevitable large hat.玛丽戴着她总是戴的那顶大帽子。
• The defeat had inevitable consequences for British policy.战败对英国政策不可避免地产生了影响。

12 tributaries   

n. 支流

参考例句：

• In such areas small tributaries or gullies will not show. 在这些地区，小的支流和冲沟显示不出来。
• These tributaries are subsequent streams which erode strike valley. 这些支流系即为蚀出走向谷的次生河。

13 metaphorical   

a.隐喻的，比喻的

参考例句：

• Here, then, we have a metaphorical substitution on a metonymic axis. 这样，我们在换喻（者翻译为转喻，一种以部分代替整体的修辞方法）上就有了一个隐喻的替代。
• So, in a metaphorical sense, entropy is arrow of time. 所以说，我们可以这样作个比喻：熵像是时间之矢。

14 conditional   

adj.条件的，带有条件的

参考例句：

• My agreement is conditional on your help.你肯帮助我才同意。
• There are two forms of most-favored-nation treatment:conditional and unconditional.最惠国待遇有两种形式:有条件的和无条件的。

15 analogous   

adj.相似的；类似的

参考例句：

• The two situations are roughly analogous.两种情況大致相似。
• The company is in a position closely analogous to that of its main rival.该公司与主要竞争对手的处境极为相似。

16 locus   

n.中心

参考例句：

• Barcelona is the locus of Spanish industry.巴塞罗那是西班牙工业中心。
• Thereafter,the military remained the locus of real power.自此之后，军方一直掌握着实权。

17 abdomen   

n.腹，下腹(胸部到腿部的部分)

参考例句：

• How to know to there is ascarid inside abdomen?怎样知道肚子里面有蛔虫？
• He was anxious about an off-and-on pain the abdomen.他因时隐时现的腹痛而焦虑。

18 puffed   

adj.疏松的v.使喷出( puff的过去式和过去分词 )；喷着汽（或烟）移动；吹嘘；吹捧

参考例句：

• He lit a cigarette and puffed at it furiously. 他点燃了一支香烟，狂吸了几口。 来自《简明英汉词典》
• He felt grown-up, puffed up with self-importance. 他觉得长大了，便自以为了不起。 来自《简明英汉词典》

19 subsiding   

v.（土地）下陷（因在地下采矿）( subside的现在分词 )；减弱；下降至较低或正常水平；一下子坐在椅子等上

参考例句：

• The flooded river was subsiding rapidly. 泛滥的河水正在迅速退落。 来自《简明英汉词典》
• Gradually the tension was subsiding, gradually the governor was relenting. 风潮渐渐地平息了。 来自汉英文学 - 家（1-26） - 家（1-26）

20 wasps   

黄蜂( wasp的名词复数 )； 胡蜂； 易动怒的人； 刻毒的人

参考例句：

• There's a wasps' nest in that old tree. 那棵老树上有一个黄蜂巢。
• We live in dread not only of unpleasant insects like spiders or wasps, but of quite harmless ones like moths. 我们不仅生活在对象蜘蛛或黄蜂这样的小虫的惧怕中，而且生活在对诸如飞蛾这样无害昆虫的惧怕中

21 inhale   

v.吸入(气体等)，吸(烟)

参考例句：

• Don't inhale dust into your lung.别把灰尘吸进肺里。
• They are pleased to not inhale second hand smoke.他们很高兴他们再也不会吸到二手烟了。

22 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。