The Works of George Berkeley Part 37

Part First

1. It is evident to any one who takes a survey of the _objects of human knowledge_, that they are either _ideas_ actually imprinted on the senses; or else such as are perceived by attending to the pa.s.sions and operations of the mind; or lastly, _ideas_ formed by help of memory and imagination-either compounding, dividing, or barely representing those originally perceived in the aforesaid ways. By sight I have the ideas of light and colours, with their several degrees and variations. By touch I perceive hard and soft, heat and cold, motion and resistance; and of all these more and less either as to quant.i.ty or degree. Smelling furnishes me with odours; the palate with tastes; and hearing conveys sounds to the mind in all their variety of tone and composition(521).

And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one _thing_. Thus, for example, a certain colour, taste, smell, figure and consistence having been observed to go together, are accounted one distinct thing, signified by the name apple; other collections of ideas const.i.tute a stone, a tree, a book, and the like sensible things; which as they are pleasing or disagreeable excite the pa.s.sions of love, hatred, joy, grief, and so forth(522).

2. But, besides all that endless variety of ideas or objects of knowledge, there is likewise Something which knows or perceives them; and exercises divers operations, as willing, imagining, remembering, about them. This perceiving, active being is what I call _mind_, _spirit_, _soul_, or _myself_. By which words I do not denote any one of my ideas, but a thing entirely distinct from them, wherein they exist, or, which is the same thing, whereby they are perceived; for the existence of an idea consists in being perceived(523).

3. That neither our thoughts, nor pa.s.sions, nor ideas formed by the imagination, exist without the mind is what everybody will allow. And to me it seems no less evident that the various sensations, or ideas imprinted on the Sense, however blended or combined together (that is, whatever objects they compose), cannot exist otherwise than in a mind perceiving them(524). I think an intuitive knowledge may be obtained of this, by any one that shall attend to what is meant by the term _exist_ when applied to sensible things(525). The table I write on I say exists; that is, I see and feel it: and if I were out of my study I should say it existed; meaning thereby that if I was in my study I might perceive it, or that some other spirit actually does perceive it. There was an odour, that is, it was smelt; there was a sound, that is, it was heard; a colour or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions(526). For as to what is said of the _absolute_ existence of unthinking things, without any relation to their being perceived, that is to me perfectly unintelligible. Their _esse_ is _percipi_; nor is it possible they should have any existence out of the minds or thinking things which perceive them(527).

4. It is indeed an opinion strangely prevailing amongst men, that houses, mountains, rivers, and in a word all sensible objects, have an existence, natural or real(528), distinct from their being perceived by the understanding. But, with how great an a.s.surance and acquiescence soever this Principle may be entertained in the world, yet whoever shall find in his heart to call it in question may, if I mistake not, perceive it to involve a manifest contradiction. For, what are the forementioned objects but the things we perceive by sense? and what do we perceive besides our own(529) ideas or sensations? and is it not plainly repugnant that any one of these, or any combination of them, should exist unperceived?

5. If we thoroughly examine this tenet(530) it will, perhaps, be found at bottom to depend on the doctrine of _abstract ideas_. For can there be a nicer strain of abstraction than to distinguish the existence of sensible objects from their being perceived, so as to conceive them existing unperceived(531)? Light and colours, heat and cold, extension and figures-in a word the things we see and feel-what are they but so many sensations, notions(532), ideas, or impressions on the sense? and is it possible to separate, even in thought, any of these from perception? For my part, I might as easily divide a thing from itself. I may, indeed, divide in my thoughts, or conceive apart from each other, those things which perhaps I never perceived by sense so divided. Thus, I imagine the trunk of a human body without the limbs, or conceive the smell of a rose without thinking on the rose itself. So far, I will not deny, I can abstract; if that may properly be called _abstraction_ which extends only to the conceiving separately such objects as it is possible may really exist or be actually perceived asunder. But my conceiving or imagining power does not extend beyond the possibility of real existence or perception. Hence, as it is impossible for me to see or feel anything without an actual sensation of that thing, so is it impossible for me to conceive in my thoughts any sensible thing or object distinct from the sensation or perception of it. [(533)In truth, the object and the sensation are the same thing, and cannot therefore be abstracted from each other.]

6. Some truths there are so near and obvious to the mind that a man need only open his eyes to see them. Such I take this important one to be, viz.

that all the choir of heaven and furniture of the earth, in a word all those bodies which compose the mighty frame of the world, have not any subsistence without a mind; that their _being_ is to be perceived or known; that consequently so long as they are not actually perceived by me, or do not exist in my mind, or that of any other created spirit, they must either have no existence at all, or else subsist in the mind of some Eternal Spirit: it being perfectly unintelligible, and involving all the absurdity of abstraction, to attribute to any single part of them an existence independent of a spirit. [(534)To be convinced of which, the reader need only reflect, and try to separate in his own thoughts the _being_ of a sensible thing from its _being perceived_.]

7. From what has been said it is evident there is not any other Substance than _Spirit_, or that which perceives(535). But, for the fuller proof(536) of this point, let it be considered the sensible qualities are colour, figure, motion, smell, taste, and such like, that is, the ideas perceived by sense. Now, for an idea to exist in an unperceiving thing is a manifest contradiction; for to have an idea is all one as to perceive: that therefore wherein colour, figure, and the like qualities exist must perceive them. Hence it is clear there can be no unthinking substance or _substratum_ of those ideas.

8. But, say you, though the ideas themselves(537) do not exist without the mind, yet there may be things like them, whereof they are copies or resemblances; which things exist without the mind, in an unthinking substance(538). I answer, an idea can be like nothing but an idea; a colour or figure can be like nothing but another colour or figure. If we look but never so little into our thoughts, we shall find it impossible for us to conceive a likeness except only between our ideas. Again, I ask whether those supposed _originals_, or external things, of which our ideas are the pictures or representations, be themselves perceivable or no? If they are, then _they_ are ideas, and we have gained our point: but if you say they are not, I appeal to any one whether it be sense to a.s.sert a colour is like something which is invisible; hard or soft, like something which is intangible; and so of the rest.

9. Some there are who make a distinction betwixt _primary_ and _secondary_ qualities(539). By the former they mean extension, figure, motion, rest, solidity or impenetrability, and number; by the latter they denote all other sensible qualities, as colours, sounds, tastes, and so forth. The ideas we have of these last they acknowledge not to be the resemblances of anything existing without the mind, or unperceived; but they will have our ideas of the _primary qualities_ to be patterns or images of things which exist without the mind, in an unthinking substance which they call Matter.

By Matter, therefore, we are to understand an inert(540), senseless substance, in which extension, figure, and motion do actually subsist. But it is evident, from what we have already shewn, that extension, figure, and motion are only ideas existing in the mind(541), and that an idea can be like nothing but another idea; and that consequently neither they nor their archetypes can exist in an unperceiving substance. Hence, it is plain that the very notion of what is called _Matter_ or _corporeal substance_, involves a contradiction in it. [(542)Insomuch that I should not think it necessary to spend more time in exposing its absurdity. But, because the tenet of the existence of Matter(543) seems to have taken so deep a root in the minds of philosophers, and draws after it so many ill consequences, I choose rather to be thought prolix and tedious than omit anything that might conduce to the full discovery and extirpation of that prejudice.]

10. They who a.s.sert that figure, motion, and the rest of the primary or original qualities(544) do exist without the mind, in unthinking substances, do at the same time acknowledge that colours, sounds, heat, cold, and suchlike secondary qualities, do not; which they tell us are sensations, existing in the mind alone, that depend on and are occasioned by the different size, texture, and motion of the minute particles of matter(545). This they take for an undoubted truth, which they can demonstrate beyond all exception. Now, if it be certain that those _original_ qualities are inseparably united with the other sensible qualities, and not, even in thought, capable of being abstracted from them, it plainly follows that _they_ exist only in the mind. But I desire any one to reflect, and try whether he can, by any abstraction of thought, conceive the extension and motion of a body without all other sensible qualities. For my own part, I see evidently that it is not in my power to frame an idea of a body extended and moving, but I must withal give it some colour or other sensible quality, which is acknowledged to exist only in the mind. In short, extension, figure and motion, abstracted from all other qualities, are inconceivable. Where therefore the other sensible qualities are, there must these be also, to wit, in the mind and nowhere else(546).

11. Again, _great_ and _small_, _swift_ and _slow_, are allowed to exist nowhere without the mind(547); being entirely relative, and changing as the frame or position of the organs of sense varies. The extension therefore which exists without the mind is neither great nor small, the motion neither swift nor slow; that is, they are nothing at all. But, say you, they are extension in general, and motion in general. Thus we see how much the tenet of extended moveable substances existing without the mind depends on that strange doctrine of _abstract ideas_. And here I cannot but remark how nearly the vague and indeterminate description of Matter, or corporeal substance, which the modern philosophers are run into by their own principles, resembles that antiquated and so much ridiculed notion of _materia prima_, to be met with in Aristotle and his followers.

Without extension solidity cannot be conceived: since therefore it has been shewn that extension exists not in an unthinking substance, the same must also be true of solidity(548).

12. That _number_ is entirely the creature of the mind(549), even though the other qualities be allowed to exist without, will be evident to whoever considers that the same thing bears a different denomination of number as the mind views it with different respects. Thus, the same extension is one, or three, or thirty-six, according as the mind considers it with reference to a yard, a foot, or an inch. Number is so visibly relative, and dependent on men's understanding, that it is strange to think how any one should give it an absolute existence without the mind.

We say one book, one page, one line, &c.; all these are equally units, though some contain several of the others. And in each instance, it is plain, the unit relates to some particular combination of ideas _arbitrarily_ put together by the mind(550).

13. Unity I know some(551) will have to be a simple or uncompounded idea, accompanying all other ideas into the mind. That I have any such idea answering the word _unity_ I do not find; and if I had, methinks I could not miss finding it; on the contrary, it should be the most familiar to my understanding, since it is said to accompany all other ideas, and to be perceived by all the ways of sensation and reflexion. To say no more, it is an _abstract idea_.

14. I shall farther add, that, after the same manner as modern philosophers prove certain sensible qualities to have no existence in Matter, or without the mind, the same thing may be likewise proved of all other sensible qualities whatsoever. Thus, for instance, it is said that heat and cold are affections only of the mind, and not at all patterns of real beings, existing in the corporeal substances which excite them; for that the same body which appears cold to one hand seems warm to another.

Now, why may we not as well argue that figure and extension are not patterns or resemblances of qualities existing in Matter; because to the same eye at different stations, or eyes of a different texture at the same station, they appear various, and cannot therefore be the images of anything settled and determinate without the mind? Again, it is proved that sweetness is not really in the sapid thing; because the thing remaining unaltered the sweetness is changed into bitter, as in case of a fever or otherwise vitiated palate. Is it not as reasonable to say that motion is not without the mind; since if the succession of ideas in the mind become swifter, the motion, it is acknowledged, shall appear slower, without any alteration in any external object(552)?

15. In short, let any one consider those arguments which are thought manifestly to prove that colours and tastes exist only in the mind, and he shall find they may with equal force be brought to prove the same thing of extension, figure, and motion. Though it must be confessed this method of arguing does not so much prove that there is no extension or colour in an outward object, as that we do not know by sense which is the true extension or colour of the object. But the arguments foregoing(553) plainly shew it to be impossible that any colour or extension at all, or other sensible quality whatsoever, should exist in an unthinking subject without the mind, or in truth that there should be any such thing as an outward object(554).

16. But let us examine a little the received opinion. It is said extension is a _mode_ or _accident_ of Matter, and that Matter is the _substratum_ that supports it. Now I desire that you would explain to me what is meant by Matter's _supporting_ extension. Say you, I have no idea of Matter; and therefore cannot explain it. I answer, though you have no positive, yet, if you have any meaning at all, you must at least have a relative idea of Matter; though you know not what it is, yet you must be supposed to know what relation it bears to accidents, and what is meant by its supporting them. It is evident _support_ cannot here be taken in its usual or literal sense, as when we say that pillars support a building. In what sense therefore must it be taken? [(555) For my part, I am not able to discover any sense at all that can be applicable to it.]

17. If we inquire into what the most accurate philosophers declare themselves to mean by _material substance_, we shall find them acknowledge they have no other meaning annexed to those sounds but the idea of Being in general, together with the relative notion of its supporting accidents.

The general idea of Being appeareth to me the most abstract and incomprehensible of all other; and as for its supporting accidents, this, as we have just now observed, cannot be understood in the common sense of those words: it must therefore be taken in some other sense, but what that is they do not explain. So that when I consider the two parts or branches which make the signification of the words _material substance_, I am convinced there is no distinct meaning annexed to them. But why should we trouble ourselves any farther, in discussing this material _substratum_ or support of figure and motion and other sensible qualities? Does it not suppose they have an existence without the mind? And is not this a direct repugnancy, and altogether inconceivable?

18. But, though it were possible that solid, figured, moveable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by Sense or by Reason(556). As for our senses, by them we have the knowledge only of our sensations, ideas, or those things that are immediately perceived by sense, call them what you will: but they do not inform us that things exist without the mind, or unperceived, like to those which are perceived. This the materialists themselves acknowledge.-It remains therefore that if we have any knowledge at all of external things, it must be by reason inferring their existence from what is immediately perceived by sense. But ((557)I do not see) what reason can induce us to believe the existence of bodies without the mind, from what we perceive, since the very patrons of Matter themselves do not pretend there is any necessary connexion betwixt them and our ideas? I say it is granted on all hands (and what happens in dreams, frensies, and the like, puts it beyond dispute) that it is possible we might be affected with all the ideas we have now, though no bodies existed without resembling them(558). Hence it is evident the supposition of external bodies(559) is not necessary for the producing our ideas; since it is granted they are produced sometimes, and might possibly be produced always, in the same order we see them in at present, without their concurrence.

19. But, though we might possibly have all our sensations without them, yet perhaps it may be thought easier to conceive and explain the manner of their production, by supposing external bodies in their likeness rather than otherwise; and so it might be at least probable there are such things as bodies that excite their ideas in our minds. But neither can this be said. For, though we give the materialists their external bodies, they by their own confession are never the nearer knowing how our ideas are produced; since they own themselves unable to comprehend in what manner body can act upon spirit, or how it is possible it should imprint any idea in the mind(560). Hence it is evident the production of ideas or sensations in our minds(561), can be no reason why we should suppose Matter or corporeal substances(562); since that is acknowledged to remain equally inexplicable with or without this supposition. If therefore it were possible for bodies to exist without the mind, yet to hold they do so must needs be a very precarious opinion; since it is to suppose, without any reason at all, that G.o.d has created innumerable beings that are entirely useless, and serve to no manner of purpose.

20. In short, if there were external bodies(563), it is impossible we should ever come to know it; and if there were not, we might have the very same reasons to think there were that we have now. Suppose-what no one can deny possible-an intelligence, without the help of external bodies, to be affected with the same train of sensations or ideas that you are, imprinted in the same order and with like vividness in his mind. I ask whether that intelligence hath not all the reason to believe the existence of Corporeal Substances, represented by his ideas, and exciting them in his mind, that you can possibly have for believing the same thing? Of this there can be no question. Which one consideration were enough to make any reasonable person suspect the strength of whatever arguments he may think himself to have, for the existence of bodies without the mind.

21. Were it necessary to add any farther proof against the existence of Matter(564), after what has been said, I could instance several of those errors and difficulties (not to mention impieties) which have sprung from that tenet. It has occasioned numberless controversies and disputes in philosophy, and not a few of far greater moment in religion. But I shall not enter into the detail of them in this place, as well because I think arguments _a posteriori_ are unnecessary for confirming what has been, if I mistake not, sufficiently demonstrated _a priori_, as because I shall hereafter find occasion to speak somewhat of them.

22. I am afraid I have given cause to think I am needlessly prolix in handling this subject. For, to what purpose is it to dilate on that which may be demonstrated with the utmost evidence in a line or two, to any one that is capable of the least reflexion? It is but looking into your own thoughts, and so trying whether you can conceive it possible for a sound, or figure, or motion, or colour to exist without the mind or unperceived.

This easy trial(565) may perhaps make you see that what you contend for is a downright contradiction. Insomuch that I am content to put the whole upon this issue:-If you can but conceive it possible for one extended moveable substance, or in general for any one idea, or anything like an idea, to exist otherwise than in a mind perceiving it(566), I shall readily give up the cause. And, as for all that compages of external bodies you contend for, I shall grant you its existence, though you cannot either give me any reason why you believe it exists, or a.s.sign any use to it when it is supposed to exist. I say, the bare possibility of your opinions being true shall pa.s.s for an argument that it is so.

23. But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park, or books existing in a closet, and n.o.body by to perceive them. I answer, you may so, there is no difficulty in it.

But what is all this, I beseech you, more than framing in your mind certain ideas which you call _books_ and _trees_, and at the same time omitting to frame the idea of any one that may perceive them? But do not you yourself perceive or think of them all the while? This therefore is nothing to the purpose: it only shews you have the power of imagining, or forming ideas in your mind; but it does not shew that you can conceive it possible the objects of your thought may exist without the mind(567). To make out this, it is necessary that you conceive them existing unconceived or unthought of; which is a manifest repugnancy. When we do our utmost to conceive the existence of external bodies(568), we are all the while only contemplating our own ideas. But the mind, taking no notice of itself, is deluded to think it can and does conceive bodies existing unthought of, or without the mind, though at the same time they are apprehended by, or exist in, itself. A little attention will discover to any one the truth and evidence of what is here said, and make it unnecessary to insist on any other proofs against the existence of _material substance_.

24. [(569)Could men but forbear to amuse themselves with words, we should, I believe, soon come to an agreement in this point.] It is very obvious, upon the least inquiry into our own thoughts, to know whether it be possible for us to understand what is meant by the _absolute existence of sensible objects in themselves_, or _without the mind_(570). To me it is evident those words mark out either a direct contradiction, or else nothing at all. And to convince others of this, I know no readier or fairer way than to entreat they would calmly attend to their own thoughts; and if by this attention the emptiness or repugnancy of those expressions does appear, surely nothing more is requisite for their conviction. It is on this therefore that I insist, to wit, that the _absolute existence of unthinking things_ are words without a meaning, or which include a contradiction. This is what I repeat and inculcate, and earnestly recommend to the attentive thoughts of the reader.

25. All our ideas, sensations, notions(571), or the things which we perceive, by whatsoever names they may be distinguished, are visibly inactive: there is nothing of power or agency included in them. So that one idea or object of thought cannot produce or make any alteration in another(572). To be satisfied of the truth of this, there is nothing else requisite but a bare observation of our ideas. For, since they and every part of them exist only in the mind, it follows that there is nothing in them but what is perceived; but whoever shall attend to his ideas, whether of sense or reflexion, will not perceive in them any power or activity; there is, therefore, no such thing contained in them. A little attention will discover to us that the very being of an idea implies pa.s.siveness and inertness in it; insomuch that it is impossible for an idea to do anything, or, strictly speaking, to be the cause of anything: neither can it be the resemblance or pattern of any active being, as is evident from sect. 8. Whence it plainly follows that extension, figure, and motion cannot be the cause of our sensations. To say, therefore, that these are the effects of powers resulting from the configuration, number, motion, and size of corpuscles(573), must certainly be false.

26. We perceive a continual succession of ideas; some are anew excited, others are changed or totally disappear. There is therefore _some_ cause of these ideas, whereon they depend, and which produces and changes them(574). That this cause cannot be any quality or idea or combination of _ideas_, is clear from the preceding section. It must therefore be a _substance_; but it has been shewn that there is no corporeal or material substance: it remains therefore that the cause of ideas is an incorporeal active substance or Spirit(575).

27. A Spirit is one simple, undivided active being-as it perceives ideas it is called the _understanding_, and as it produces or otherwise operates about them it is called the _will_. Hence there can be no _idea_ formed of a soul or spirit; for all ideas whatever, being pa.s.sive and inert (vid.

sect. 25), they cannot represent unto us, by way of image or likeness, that which acts. A little attention will make it plain to any one, that to have an idea which shall be _like_ that active Principle of motion and change of ideas is absolutely impossible. Such is the nature of Spirit, or that which acts, that it cannot be of itself perceived, but only by the effects which it produceth(576). If any man shall doubt of the truth of what is here delivered, let him but reflect and try if he can frame the idea of any power or active being; and whether he has ideas of two princ.i.p.al powers, marked by the names _will_ and _understanding_, distinct from each other, as well as from a third idea of Substance or Being in general, with a relative notion of its supporting or being the subject of the aforesaid powers-which is signified by the name _soul_ or _spirit_.

This is what some hold; but, so far as I can see, the words _will_, [(577)_understanding_, _mind_,] _soul_, _spirit_, do not stand for different ideas, or, in truth, for any idea at all, but for something which is very different from ideas, and which, being an agent, cannot be like unto, or represented by, any idea whatsoever. [(578)Though it must be owned at the same time that we have some _notion_ of soul, spirit, and the operations of the mind, such as willing, loving, hating-inasmuch as we know or understand the meaning of these words.]

28. I find I can excite ideas(579) in my mind at pleasure, and vary and shift the scene as oft as I think fit. It is no more than _willing_, and straightway this or that idea arises in my fancy; and by the same power it is obliterated and makes way for another. This making and unmaking of ideas doth very properly denominate the mind active. Thus much is certain and grounded on experience: but when we talk of unthinking agents, or of exciting ideas exclusive of volition, we only amuse ourselves with words(580).

29. But, whatever power I may have over my own thoughts, I find the ideas actually perceived by Sense have not a like dependence on _my_ will. When in broad daylight I open my eyes, it is not in my power to choose whether I shall see or no, or to determine what particular objects shall present themselves to my view: and so likewise as to the hearing and other senses; the ideas imprinted on them are not creatures of _my_ will(581). There is therefore some other Will or Spirit that produces them.

30. The ideas of Sense are more strong, lively, and distinct than those of the Imagination(582); they have likewise a steadiness, order, and coherence, and are not excited at random, as those which are the effects of human wills often are, but in a regular train or series-the admirable connexion whereof sufficiently testifies the wisdom and benevolence of its Author. Now the set rules, or established methods, wherein the Mind we depend on excites in us the ideas of Sense, are called _the laws of nature_; and these we learn by experience, which teaches us that such and such ideas are attended with such and such other ideas, in the ordinary course of things.

31. This gives us a sort of foresight, which enables us to regulate our actions for the benefit of life. And without this we should be eternally at a loss: we could not know how to act anything that might procure us the least pleasure, or remove the least pain of sense. That food nourishes, sleep refreshes, and fire warms us; that to sow in the seed-time is the way to reap in the harvest; and in general that to obtain such or such ends, such or such means are conducive-all this we know, not by discovering any _necessary connexion_ between our ideas, but only by the observation of the _settled laws_ of nature; without which we should be all in uncertainty and confusion, and a grown man no more know how to manage himself in the affairs of life than an infant just born(583).

32. And yet this consistent uniform working, which so evidently displays the Goodness and Wisdom of that Governing Spirit whose Will const.i.tutes the laws of nature, is so far from leading our thoughts to Him, that it rather sends them wandering after second causes(584). For, when we perceive certain ideas of Sense constantly followed by other ideas, and we know this is not of our own doing, we forthwith attribute power and agency to the ideas themselves, and make one the cause of another, than which nothing can be more absurd and unintelligible. Thus, for example, having observed that when we perceive by sight a certain round luminous figure, we at the same time perceive by touch the idea or sensation called heat, we do from thence conclude the sun to be the _cause_ of heat. And in like manner perceiving the motion and collision of bodies to be attended with sound, we are inclined to think the latter the _effect_ of the former(585).

33. The ideas imprinted on the Senses by the Author of nature are called _real things_: and those excited in the imagination, being less regular, vivid, and constant, are more properly termed _ideas_ or _images of_ things, which they copy and represent. But then our _sensations_, be they never so vivid and distinct, are nevertheless ideas(586): that is, they exist in the mind, or are perceived by it, as truly as the ideas of its own framing. The ideas of Sense are allowed to have more reality(587) in them, that is, to be more strong, orderly, and coherent than the creatures of the mind; but this is no argument that they exist without the mind.

They are also less dependent on the spirit or thinking substance which perceives them, in that they are excited by the will of another and more powerful Spirit; yet still they are _ideas_: and certainly no idea, whether faint or strong, can exist otherwise than in a mind perceiving it(588).

34. Before we proceed any farther it is necessary we spend some time in answering Objections(589) which may probably be made against the Principles we have hitherto laid down. In doing of which, if I seem too prolix to those of quick apprehensions, I desire I may be excused, since all men do not equally apprehend things of this nature; and I am willing to be understood by every one.