3.1: First Dialogue

Philonous: Good morning, Hylas: I didn’t expect to find you out and about so early.

Hylas: It is indeed somewhat unusual: but my thoughts were so taken up with a subject I was talking about last night that I couldn’t sleep, so I decided to get up and walk in the garden.

Phil: That’s good! It gives you a chance to see what innocent and agreeable pleasures you lose every morning. Can there be a pleasanter time of the day, or a more delightful season of the year? That purple sky, those wild but sweet notes of birds, the fragrant bloom on the trees and flowers, the gentle influence of the rising sun, these and a thousand nameless beauties of nature inspire the soul with secret raptures. But I’m afraid I am interrupting your thoughts; for you seemed very intent on something.

Hyl: Yes, I was, and I’d be grateful if you would allow me to carry on with it. But I don’t in the least want to deprive myself of your company, for my thoughts always flow more easily in conversation with a friend than when I am alone. Please, may I share with you the thoughts I have been having?

Phil: With all my heart! It is what I would have requested myself, if you hadn’t asked first.

Hyl: I was considering the odd fate of those men who have in all ages, through a desire to mark themselves off from the common people or through heaven knows what trick of their thought, claimed either to believe nothing at all or to believe the most extravagant things in the world. This wouldn’t matter so much if their paradoxes and scepticism didn’t bring consequences that are bad for mankind in general. But there’s a risk that they will do that, and that when men who are thought to have spent their whole time in the pursuit of knowledge claim to be entirely ignorant of everything, or advocate views that are in conflict with plain and commonly accepted principles, this will tempt other people—who have less leisure for this sort of thing—to become suspicious of the most important truths, ones they had previously thought to be sacred and unquestionable.

Phil: I entirely agree with you about the bad effects of the paraded doubts of some philosophers and the fantastical views of others. I have felt this so strongly in recent times that I have dropped some of the high-flown theories I had learned in their universities, replacing them with ordinary common opinions. Since this revolt of mine against metaphysical notions and in favour of the plain dictates of nature and common sense, I swear that I find I can think ever so much better, so that I can now easily understand many things which previously were mysteries and riddles.

Hyl: I am glad to find there was nothing in the accounts I heard of you.

Phil: What, if you please, were they?

Hyl: In last night’s conversation you were represented as someone who maintains the most extravagant opinion that ever entered into the mind of man, namely that there is no such thing as material substance in the world.

Phil: I seriously believe that there is no such thing as what philosophers call ‘material substance’; but if I were made to see anything absurd or sceptical in this, then I would have the same reason to renounce this belief as I think I have now to reject the contrary opinion.

Hyl: What! can anything be more fantastical, more in conflict with common sense, or a more obvious piece of scepticism, than to believe there is no such thing as matter?

Phil: Steady on, Hylas! What if it were to turn out that you who hold that there is matter are—by virtue of that opinion—a greater sceptic, and maintain more paradoxes and conflicts with common sense, than I who believe no such thing?

Hyl: You have as good a chance of convincing me that the part is greater than the whole as of convincing me that I must give up my belief in matter if I am to avoid absurdity and scepticism.

Phil: Well then, are you content to accept as true any opinion that turns out to be the most agreeable to common sense, and most remote from scepticism?

Hyl: With all my heart. Since you want to start arguments about the plainest things in the world, I am content for once to hear what you have to say.

Phil: Tell me, please, Hylas: what do you mean by a ‘sceptic’?

Hyl: I mean what everyone means, ‘someone who doubts everything’.

Phil: So if someone has no doubts concerning some particular point, then with regard to that point he cannot be thought a sceptic.

Hyl: I agree with you.

Phil: Does doubting consist in accepting the affirmative or the negative side of a question?

Hyl: Neither. Anyone who understands English must know that doubting signifies a suspense between the two sides.

Phil: So if someone denies any point, he can no more be said to doubt concerning it than he who affirms it with the same degree of assurance.

Hyl: True.

Phil: And so his denial no more makes him a sceptic than the other is.

Hyl: I acknowledge it.

Phil: Then how does it happen, Hylas, that you call me a sceptic because I deny what you affirm, namely the existence of matter? For all you know, I may be as firmly convinced in my denial as you are in your affirmation.

Hyl: Hold on a moment, Philonous. My definition of ‘sceptic’ was wrong; but you can’t hold a man to every false step he makes in conversation. I did say that a sceptic is someone who doubts everything; but I should have added, ‘. . . or who denies the reality and truth of things’.

Phil: What things? Do you mean the principles and theorems of sciences? But these, you know, are universal intellectual notions, and have nothing to do with matter, so that the denial of matter doesn’t imply the denial of them.

Hyl: I agree about that. But what about other things? What do you think about distrusting the senses, denying the real existence of sensible things, or claiming to know nothing of them? Isn’t that enough to qualify a man as a sceptic? [Throughout the Dialogues, ‘sensible’ means ‘capable of being sensed’—that is, visible or audible or tangible etc.]

Phil: Well, then, let us see which of us it is that denies the reality of sensible things, or claims to have the greatest ignorance of them; since, if I understand you rightly, he is to be counted the greater sceptic.

Hyl: That is what I desire.

Phil: What do you mean by ‘sensible things’?

Hyl: Things that are perceived by the senses. Can you imagine that I mean anything else?

Phil: I’m sorry, but it may greatly shorten our enquiry if I have a clear grasp of your notions. Bear with me, then, while I ask you this further question. Are things ‘perceived by the senses’ only the ones that are perceived immediately? Or do they include things that are perceived mediately, that is, through the intervention of something else?

Hyl: I don’t properly understand you.

Phil: In reading a book, what I immediately perceive are the letters ·on the page·, but mediately or by means of these the notions of God, virtue, truth, etc. are suggested to my mind. Now, there’s no doubt that •the letters are truly sensible things, or things perceived by sense; but I want to know whether you take •the things suggested by them to be ‘perceived by sense’ too.

Hyl: No, certainly, it would be absurd to think that God or virtue are sensible things, though they may be signified and suggested to the mind by sensible marks with which they have an arbitrary connection. Phil: It seems then, that by ‘sensible things’ you mean only those that can be perceived immediately by sense.

Hyl: Right.

Phil: Doesn’t it follow from this that when I see one part of the sky red and another blue, and I infer from this that there must be some cause for that difference of colours, that cause cannot be said to be a ‘sensible thing’ or perceived by eyesight?

Hyl: It does.

Phil: Similarly, when I hear a variety of sounds I cannot be said to hear their causes.

Hyl: You cannot.

Phil: And when by touch I feel a thing to be hot and heavy, I can’t say with any truth or correctness that I feel the cause of its heat or weight.

Hyl: To head off any more questions of this kind, I tell you once and for all that by ‘sensible things’ I mean only things that are perceived by sense, and that the senses perceive only what they perceive immediately; because they don’t make inferences. So the deducing of causes or occasions from effects and appearances (which are the only things we perceive by sense) is entirely the business of reason. [In this context, ‘occasion’ can be taken as equivalent to ‘cause’. The two terms are separated in the Second Dialogue at page 35.]

Phil: We agree, then, that sensible things include only things that are immediately perceived by sense. Now tell me whether we immediately perceive by sight anything besides light, colours, and shapes; by hearing anything but sounds; by the palate anything besides tastes; by the sense of smell anything besides odours; by touch anything more than tangible qualities.

Hyl: We do not.

Phil: So it seems that if you take away all sensible qualities there is nothing left that is sensible.

Hyl: I agree.

Phil: Sensible things, then, are nothing but so many sensible qualities, or combinations of sensible qualities.

Hyl: Nothing else.

Phil: So heat is a sensible thing.

Hyl: Certainly. Phil: Does the reality of sensible things consist in being perceived? or is it something different from their being perceived—something that doesn’t involve the mind?

Hyl: To exist is one thing, and to be perceived is another.

Phil: I am talking only about sensible things. My question is: By the ‘real existence’ of one of them do you mean an existence exterior to the mind and distinct from their being perceived?

Hyl: I mean a real absolute existence—distinct from, and having no relation to, their being perceived.

Phil: So if heat is granted to have a real existence, it must exist outside the mind.

Hyl: It must.

Phil: Tell me, Hylas, is this real existence equally possible for all degrees of heat that we feel; or is there a reason why we should attribute it to some degrees of heat and not to others? If there is, please tell me what it is.

Hyl: Whatever degree of heat we perceive by sense we can be sure exists also in the object that occasions it.

Phil: What, the greatest as well as the least?

Hyl: Yes, because the same reason holds for both: they are both perceived by sense; indeed, the greater degree of heat is more ·intensely· sensibly perceived; so if there is any difference it is that we are more certain of the real existence of a greater heat than we can be of the reality of a lesser.

Phil: But isn’t the most fierce and intense degree of heat a very great pain?

Hyl: No-one can deny that.

Phil: And can any unperceiving thing have pain or pleasure?

Hyl: Certainly not.

Phil: Is your material substance a senseless thing or does it have sense and perception?

Hyl: It is senseless, without doubt.

Phil: So it can’t be the subject of pain.

Hyl: Indeed it can’t.

Phil: Nor, consequently, can it be the subject of the greatest heat perceived by sense, since you agree that this is a considerable pain.

Hyl: I accept that.

Phil: Then what are we to say about your external object? Is it a material substance, or is it not?

Hyl: It is a material substance with the sensible qualities inhering in it.

Phil: But then how can a great heat exist in it, since you agree it cannot exist in a material substance? Please clear up this point.

Hyl: Hold on, Philonous! I’m afraid I went wrong in granting that intense heat is a pain. I should have said not that the pain is the heat but that it is the consequence or effect of the heat.

Phil: When you put your hand near the fire, do you feel one simple uniform sensation or two distinct sensations?

Hyl: Just one simple sensation.

Phil: Isn’t the heat immediately perceived?

Hyl: It is.

Phil: And the pain?

Hyl: True.

Phil: Well, then, seeing that they are both immediately perceived at the same time, and that the fire affects you with only one simple or uncompounded idea [= one idea without parts], it follows that this one simple idea is both the immediately perceived intense heat and the pain; and consequently, that the immediately perceived intense heat is identical with a particular sort of pain.

Hyl: It seems so.

Phil: Consult your thoughts again,

Hylas: can you conceive an intense sensation to occur without pain or pleasure?

Hyl: I cannot.

Phil: Or can you form an idea of sensible pain or pleasure in general, abstracted from every particular idea of heat, cold, tastes, smells, etc.?

Hyl: I don’t find that I can.

Phil: Then doesn’t it follow that sensible pain is nothing but intense degrees of those sensations or ideas?

Hyl: That is undeniable. In fact, I’m starting to suspect that a very great heat can’t exist except in a mind perceiving it.

Phil: What! are you then in that sceptical state of suspense, between affirming and denying?

Hyl: I think I can be definite about it. A very violent and painful heat can’t exist outside the mind.

Phil: So according to you it has no real existence.

Hyl: I admit it.

Phil: Is it certain, then, that no body in nature is really hot?

Hyl: I haven’t said that there is no real heat in bodies. I only say that there’s no such thing as an intense real heat ·in bodies·.

Phil: But didn’t you say earlier that all degrees of heat are equally real, or that if there is any difference the greater heat is more certainly real than the lesser?

Hyl: Yes, I did; but that was because I had overlooked the reason there is for distinguishing between them, which I now plainly see. It is this: because •intense heat is nothing but a particular kind of painful sensation, and •pain can’t exist except in a perceiving being, it follows that •no intense heat can really exist in an unperceiving corporeal [= ‘bodily’] substance. But that’s no reason for denying that less intense heat can exist in such a substance.

Phil: But how are we to draw the line separating degrees of heat that exist only in the mind from ones that exist outside it?

Hyl: That isn’t hard. The slightest pain can’t exist unperceived, as you know; so any degree of heat that is a pain exists only in the mind. We don’t have to think the same for degrees of heat that are not pains.

Phil: I think you agreed a while back that no unperceiving being is capable of pleasure, any more than it is of pain.

Hyl: I did.

Phil: Well, isn’t warmth—a milder degree of heat than what causes discomfort or worse—a pleasure?

Hyl: What of it?

Phil: It follows that warmth can’t exist outside the mind in any unperceiving substance, or body.

Hyl: So it seems.

Phil: So ·we have reached the position that· degrees of heat that aren’t painful and also ones that are can exist only in a thinking substance! Can’t we conclude from this that external bodies are absolutely incapable of any degree of heat whatsoever?

Hyl: On second thoughts, I am less sure that warmth is a pleasure than I am that intense heat is a pain.

Phil: I don’t claim that warmth is as •great a pleasure as heat is a pain. But if you admit it to be even a •small pleasure, that is enough to yield my conclusion.

Hyl: I could rather call it ‘absence of pain’. It seems to be merely the lack of pain and of pleasure. I hope you won’t deny that this quality or state is one that an unthinking substance can have!

Phil: If you are determined to maintain that warmth is not a pleasure, I don’t know how to convince you otherwise except by appealing to your own experience. But what do you think about cold?

Hyl: The same as I do about heat. An intense degree of cold is a pain; for to feel a very great cold is to experience a great discomfort, so it can’t exist outside the mind. But a lesser degree of cold can exist outside the mind, as well as a lesser degree of heat.

Phil: So when we feel a moderate degree of heat (or cold) from a body that is applied to our skin, we must conclude that that body has a moderate degree of heat (or cold) in it?

Hyl: We must.

Phil: Can any doctrine be true if it necessarily leads to absurdity?

Hyl: Certainly not.

Phil: Isn’t it an absurdity to think that a single thing should be at the same time both cold and warm?

Hyl: It is.

Phil: Well, now, suppose that one of your hands is hot and the other cold, and that they are both at once plunged into a bowl of water that has a temperature between the two. Won’t the water seem cold to one hand and warm to the other?

Hyl: It will.

Phil: Then doesn’t it follow by your principles that the water really is both cold and warm at the same time—thus believing something that you agree to be an absurdity?

Hyl: I admit that that seems right.

Phil: So the principles themselves are false, since you have admitted that no true principle leads to an absurdity.

Hyl: But, after all, can anything be more absurd than to say that there is no heat in the fire?

Phil: To make the point still clearer, answer me this: in two cases that are exactly alike, oughtn’t we to make the same judgment?

Hyl: We ought.

Phil: When a pin pricks your finger, doesn’t it tear and divide the fibres of your flesh?

Hyl: It does.

Phil: And when hot coal burns your finger, does it do any more?

Hyl: It does not.

Phil: You hold that the pin itself doesn’t contain either the sensation that it causes, or anything like it. So, given what you have just agreed to—·namely that like cases should be judged alike·—you ought to hold that the fire doesn’t contain either •the sensation that it causes or •anything like it.

Hyl: Well, since it must be so, I am content to give up this point, and admit that heat and cold are only sensations existing in our minds. Still, there are plenty of other qualities through which to secure the reality of external things.

Phil: But what will you say, Hylas, if it turns out that the same argument applies with regard to all other sensible qualities, and that none of them can be supposed to exist outside the mind, any more than heat and cold can?

Hyl: Proving that would be quite a feat, but I see no chance of your doing so.

Phil: Let us examine the other sensible qualities in order. What about tastes? Do you think they exist outside the mind, or not?

Hyl: Can anyone in his right mind doubt that sugar is sweet, or that wormwood is bitter?

Phil: Tell me, Hylas: is a sweet taste a particular kind of pleasure or pleasant sensation, or is it not?

Hyl: It is.

Phil: And isn’t bitterness some kind of discomfort or pain?

Hyl: I grant that.

Phil: If therefore sugar and wormwood are unthinking corporeal substances existing outside the mind, how can sweetness and bitterness—that is, pleasure and pain—be in them?

Hyl: Hold on, Philonous! Now I see what has deluded me all this time. You asked whether heat and cold, sweetness and bitterness, are particular sorts of pleasure and pain; to which I answered simply that they are. I should have answered by making a distinction: those qualities as perceived by us are pleasures or pains, but as existing in the external objects they are not. So we cannot conclude without qualification that there is no heat in the fire or sweetness in the sugar, but only that heat or sweetness as perceived by us are not in the fire or the sugar. What do you say to this?

Phil: I say it is irrelevant. We were talking only about ‘sensible things’, which you defined as things we immediately perceive by our senses. Whatever other qualities you are talking about have no place in our conversation, and I don’t know anything about them. You may indeed claim to have discovered certain qualities that you don’t perceive, and assert that they exist in fire and sugar; but I can’t for the life of me see how that serves your side in the argument we were having. Tell me then once more, do you agree that heat and cold, sweetness and bitterness (meaning the qualities that are perceived by the senses), don’t exist outside the mind?

Hyl: I see it is no use holding out, so I give up the cause with respect to those four qualities. Though I must say it sounds odd to say that sugar isn’t sweet.

Phil: It might sound better to you if you bear this in mind: someone whose palate is diseased may experience as bitter stuff that at other times seems sweet to him. And it’s perfectly obvious that different people perceive different tastes in the same food, since what one man delights in another loathes. How could this be, if the taste were really inherent in the food?

Hyl: I admit that I don’t know how.

Phil: Now think about odours. Don’t they exactly fit what I have just been saying about tastes? Aren’t they just so many pleasing or displeasing sensations?

Hyl: They are.

Phil: Then can you conceive it to be possible that they should exist in an unperceiving thing?

Hyl: I cannot.

Phil: Or can you imagine that filth and excrement affect animals that choose to feed on them with the same smells that we perceive in them?

Hyl: By no means.

Phil: Then can’t we conclude that smells, like the other qualities we have been discussing, cannot exist anywhere but in a perceiving substance or mind?

Hyl: I think so.

Phil: What about sounds? Are they qualities really inherent in external bodies, or not?

Hyl: They don’t inhere in the sounding bodies. We know this, because when a bell is struck in a vacuum, it sends out no sound. So the subject of sound must be the air.

Phil: Explain that, Hylas.

Hyl: When the air is set into motion, we perceive a louder or softer sound in proportion to the air’s motion; but when the air is still, we hear no sound at all.

Phil: Granting that we never hear a sound except when some motion is produced in the air, I still don’t see how you can infer from this that the sound itself is in the air.

Hyl: This motion in the external air is what produces in the mind the sensation of sound. By striking on the ear-drum it causes a vibration which is passed along the auditory nerves to the brain, whereon the mind experiences the sensation called sound.

Phil: What! is sound a sensation?

Hyl: As I said: as perceived by us it is a particular sensation in the mind.

Phil: And can any sensation exist outside the mind?

Hyl: No, certainly.

Phil: But if sound is a sensation, how can it exist in the air, if by ‘the air’ you mean a senseless substance existing outside the mind?

Hyl: Philonous, you must distinguish sound as it is perceived by us from sound as it is in itself; or—in other words—distinguish the sound we immediately perceive from the sound that exists outside us. The former is indeed a particular kind of sensation, but the latter is merely a vibration in the air.

Phil: I thought I had already flattened that distinction by the answer I gave when you were applying it in a similar case before. But I’ll let that pass. Are you sure, then, that sound is really nothing but motion?

Hyl: I am.

Phil: Whatever is true of real sound, therefore, can truthfully be said of motion.

Hyl: It may.

Phil: So it makes sense to speak of motion as something that is loud, sweet, piercing, or low-pitched!

Hyl: I see you are determined not to understand me. Isn’t it obvious that those qualities belong only to sensible sound, or ‘sound’ in the ordinary everyday meaning of the word, but not to ‘sound’ in the real and scientific sense, which (as I have just explained) is nothing but a certain motion of the air?

Phil: It seems, then, there are two sorts of sound—the common everyday sort that we hear, and the scientific and real sort ·that we don’t hear·.

Hyl: Just so.

Phil: And the latter kind of sound consists in motion.

Hyl: As I told you.

Phil: Tell me, Hylas, which of the senses do you think the idea of motion belongs to? The sense of hearing?

Hyl: Certainly not. To the senses of sight and touch.

Phil: It should follow then, according to you, that real sounds may possibly be seen or felt, but can never be heard.

Hyl: Look, Philonous, make fun of my views if you want to, but that won’t alter the truth of things. I admit that the inferences you draw from them sound a little odd; but ordinary language is formed by ordinary people for their own use, so it’s not surprising if statements that express exact scientific notions seem clumsy and strange.

Phil: Is it come to that? I assure you, I think I have scored a pretty big win when you so casually depart from ordinary phrases and opinions; because what we were mainly arguing about was whose notions are furthest from the common road and most in conflict with what people in general think. Your claim that real sounds are never heard, and that we get our idea of sound through some other sense—can you think that this is merely an odd-sounding scientific truth? Isn’t something in it contrary to nature and the truth of things?

Hyl: Frankly, I don’t like it either. Given the concessions I have already made, I had better admit that sounds also have no real existence outside the mind.

Phil: And I hope you won’t stick at admitting the same of colours.

Hyl: Pardon me; the case of colours is very different. Can anything be more obvious than the fact that we see colours on the objects?

Phil: The objects you speak of are, I suppose, corporeal substances existing outside the mind.

Hyl: They are.

Phil: And they have true and real colours inhering in them?

Hyl: Each visible object has the colour that we see in it.

Phil: Hah! is there anything visible other than what we perceive by sight?

Hyl: There is not.

Phil: And do we perceive anything by our senses that we don’t perceive immediately?

Hyl: How often do I have to say it? I tell you, we do not.

Phil: Bear with me, Hylas, and tell me yet again whether anything is immediately perceived by the senses other than sensible qualities. I know you asserted that nothing is; but I want to know now whether you still think so.

Hyl: I do.

Phil: Now, is your corporeal substance either a sensible quality or made up of sensible qualities?

Hyl: What a question to ask! Who ever thought it was?

Phil: Here is why I ask. When you say that each visible object has the colour that we see in it, you imply that either (1) visible objects are sensible qualities, or else (2) something other than sensible qualities can be perceived by sight. But we earlier agreed that (2) is false, and you still think it is; ·so we are left with the thesis (1) that visible objects are sensible qualities·. Now, in this conversation you have been taking it that visible objects are corporeal substances; and so we reach the conclusion that your corporeal substances are nothing but sensible qualities.

Hyl: You may draw as many absurd consequences as you please, and try to entangle the plainest things; but you will never persuade me out of my senses. I clearly understand my own meaning.

Phil: I wish you would make me understand it too! But since you don’t want me to look into your notion of corporeal substance, I shall drop that point. But please tell me whether the colours that we see are •the very ones that exist in external bodies or •some other colours.

Hyl: They are the very same ones.

Phil: Oh! Then are the beautiful red and purple that we see on those clouds over there really in them? Or do you ·rather· think that the clouds in themselves are nothing but a dark mist or vapour?

Hyl: I must admit, Philonous, that those colours aren’t really in the clouds as they seem to be at this distance. They are only apparent colours.

Phil: Apparent call you them? How are we to distinguish these apparent colours from real ones?

Hyl: Very easily. When a colour appears only at a distance, and vanishes when one comes closer, it is merely apparent.

Phil: And I suppose that real colours are ones that are revealed by looking carefully from close up?

Hyl: Right.

Phil: Does the closest and most careful way of looking use a microscope, or only the naked eye?

Hyl: A microscope, of course.

Phil: But a microscope often reveals colours in an object different from those perceived by unassisted sight. And if we had microscopes that could magnify to as much as we liked, it is certain that no object whatsoever when seen through them would appear with the same colour that it presents to the naked eye.

Hyl: Well, what do you conclude from that? You can’t argue that there are really and naturally no colours on objects, just because we can contrive artificial ways to alter them or make them vanish.

Phil: It can obviously be inferred from your own concessions, I think, that all the colours we see with our naked eyes are only apparent—like those on the clouds—since they vanish when one looks more closely and accurately, as one can with a microscope. And to anticipate your next objection I ask you whether the real and natural state of an object is revealed better by a very sharp and piercing sight, or by one that is less sharp.

Hyl: By the former, without doubt.

Phil: Isn’t it plain from ·the science of· optics that microscopes make the sight more penetrating, and represent objects as they would appear to the eye if it were naturally endowed with extreme sharpness?

Hyl: It is.

Phil: So the microscopic representation of a thing should be regarded as the one that best displays the thing’s real nature, or what the thing is in itself. so the colours perceived through a microscope are more genuine and real than those perceived in any other way.

Hyl: I admit that there’s something in what you say.

Phil: Besides, it’s not only possible but clearly true that there actually are animals whose eyes are naturally formed to perceive things that are too small for us to see. What do you think about those inconceivably small animals that we perceive through microscopes? Must we suppose they are all totally blind? If they can see, don’t we have to suppose that their sight has the same use in preserving their bodies from injuries as eyesight does in all other animals? If it does have that use, isn’t it obvious that they must see particles that are smaller than their own bodies, which will present them with a vastly different view of each object from the view that strikes our senses? Even our own eyes don’t always represent objects to us in the same way. Everyone knows that to someone suffering from jaundice all things seem yellow. So isn’t it highly probable that animals whose eyes we see to be differently structured from ours, and whose bodily fluids are unlike ours, don’t see the same colours as we do in every object? From all of this, shouldn’t it seem to follow that all colours are equally •apparent, and that none of the ones that we see are •really in any outer object?

Hyl: It should.

Phil: To put it past all doubt, consider the following. If colours were real properties or qualities inhering in external bodies, they couldn’t be altered except by some alteration in the very bodies themselves: but isn’t it evident that the colours of an object can be changed or made to disappear entirely through the use of a microscope, or some change in the fluids in the eye, or a change in the viewing distance, without any sort of real alteration in the thing itself? Indeed, even when all the other factors remain unaltered some objects present different colours to the eye depending on the angle from which they are looked at. The same thing happens when we view an object in different brightnesses of light. And everyone knows that the same bodies appear differently coloured by candle-light from what they do in daylight. Add to these facts our experience of a prism, which separates the different rays of light and thereby alters the colour of an object, causing the whitest object to appear deep blue or red to the naked eye. Now tell me whether you still think that each body has its true, real colour inhering in it. If you think it has, I want to know what •particular distance and orientation of the object, what •special condition of the eye, what •intensity or kind of light is needed for discovering that true colour and distinguishing it from the apparent ones.

Hyl: I admit to being quite convinced that they are all equally apparent, that no such thing as colour really inheres in external bodies, and that colour is wholly in the light. What confirms me in this opinion is the fact that colours are more or less vivid depending on the brightness of the light, and that when there is no light no colours are seen. Furthermore, if there were colours in external objects, how could we possibly perceive them? No external body affects the mind unless it acts first on our sense-organs; and the only action of bodies is motion, and this can’t be communicated except in collisions. So a distant object can’t act on the eye, and so can’t enable itself or its properties to be perceived by the mind. From this it plainly follows that what immediately causes the perception of colours is some substance that is in contact with the eye—such as light.

Phil: What? Is light a substance?

Hyl: I tell you, Philonous, external light is simply a thin fluid substance whose tiny particles, when agitated with a brisk motion and in various ways reflected to the eyes from the different surfaces of outer objects, cause different motions in the optic nerves; these motions are passed along to the brain, where they cause various states and events; and these are accompanied by the sensations of red, blue, yellow, etc.

Phil: It seems, then, that all the light does is to shake the optic nerves.

Hyl: That is all.

Phil: And as a result of each particular motion of the nerves the mind is affected with a sensation, which is some particular colour.

Hyl: Right.

Phil: And these sensations have no existence outside the mind.

Hyl: They have not.

Phil: Then how can you say that colours are in the light, since you take light to be a corporeal substance external to the mind?

Hyl: Light and colours as immediately perceived by us cannot exist outside the mind. I admit that. But in themselves they are only the motions and arrangements of certain insensible particles of matter.

Phil: Colours then, in the ordinary sense—that is, understood to be the immediate objects of sight—cannot be had by any substance that doesn’t perceive.

Hyl: That is what I say.

Phil: Well, then, you give up your position as regards those sensible qualities which are what all mankind takes to be colours. Think what you like about the scientists’ invisible colours; it is not my business to argue about them. But I suggest that you consider whether it is wise for you, in a discussion like this one, to affirm that the red and blue we see are not real colours, and that certain unknown motions and shapes which no man ever did or could see are real colours. Aren’t these shocking notions, and aren’t they open to as many ridiculous inferences as those you had to give up in the case of sounds?

Hyl: I have to admit, Philonous, that I can’t keep this up any longer. Colours, sounds, tastes—in a word, all that are termed ‘secondary qualities’—have no existence outside the mind. But in granting this I don’t take anything away from the reality of matter or external objects, because various philosophers maintain what I just did about secondary qualities and yet are the far from denying matter. [In this context, ‘philosophers’ means ‘philosophers and scientists’.] To make this clearer: philosophers divide sensible qualities into primary and secondary. •Primary qualities are extendedness, shape, solidity, gravity, motion, and rest. They hold that these really exist in bodies. •Secondary qualities are all the sensible qualities that aren’t primary; and the philosophers assert that these are merely sensations or ideas existing nowhere but in the mind. No doubt you are already aware of all this. For my part, I have long known that such an opinion was current among philosophers, but I was never thoroughly convinced of its truth till now.

Phil: So you still believe that extension and shapes are inherent in external unthinking substances? [Here ‘extension’ could mean ‘extendedness’ or it could mean ‘size’.]

Hyl: I do.

Phil: But what if the arguments that are brought against secondary qualities hold against these also?

Hyl: Why, then I shall have to think that shape and extension also exist only in the mind.

Phil: Is it your opinion that the very shape and extension that you perceive by sense exist in the outer object or material substance?

Hyl: It is.

Phil: Have all other animals as good reason as you do to think that the shape and extension that they see and feel is in the outer object?

Hyl: Surely they do, if they can think at all.

Phil: Tell me, Hylas, do you think that the senses were given to all animals for their preservation and well-being in life? or were they given only to men for that end?

Hyl: I don’t doubt that they have the same use in all other animals.

Phil: If so, mustn’t their senses enable them to perceive their own limbs, and to perceive bodies that are capable of harming them?

Hyl: Certainly.

Phil: A tiny insect, therefore, must be supposed to see its own foot, and other things of that size or even smaller, seeing them all as bodies of considerable size, even though you can see them—if at all—only as so many visible points.

Hyl: I can’t deny that.

Phil: And to creatures even smaller than that insect they will seem even bigger.

Hyl: They will.

Phil: So that something you can hardly pick out ·because it is so small· will appear like a huge mountain to an extremely tiny animal.

Hyl: I agree about all this.

Phil: Can a single thing have different sizes at the same time?

Hyl: It would be absurd to think so.

Phil: But from what you have said it follows that the true size of the insect’s foot is •the size you see it having and •the size the insect sees it as having, and •all the sizes it is seen as having by animals that are even smaller. That is to say, your own principles have led you into an absurdity.

Hyl: I seem to be in some difficulty about this.

Phil: Another point: didn’t you agree that no real inherent property of any object can be changed unless the thing itself alters?

Hyl: I did.

Phil: But as we move towards or away from an object, its visible size varies, being at one distance ten or a hundred times greater than at another. Doesn’t it follow from this too that size isn’t really inherent in the object?

Hyl: I admit that I don’t know what to think.

Phil: You will soon be able to make up your mind, if you will venture to think as freely about this quality as you have about the others. Didn’t you admit that it was legitimate to infer that neither heat nor cold was in the water from the premise that the water seemed warm to one hand and cold to the other?

Hyl: I did.

Phil: Isn’t it the very same reasoning to infer that there is no size or shape in an object from the premise that to one eye it seems little, smooth, and round, while to the other eye it appears big, uneven, and angular?

Hyl: The very same. But does the latter ever happen?

Phil: You can at any time find out that it does, by looking with one eye bare and with the other through a microscope.

Hyl: I don’t know how to maintain it, yet I am reluctant to give up extension [= ‘size’], because I see so many odd consequences following from the concession that extension isn’t in the outer object.

Phil: Odd, you say? After the things you have already agreed to, I hope you won’t be put off from anything just because it is odd! But in any case wouldn’t it seem very odd if the general reasoning that covers all the other sensible qualities didn’t apply also to extension? If you agree that no idea or anything like an idea can exist in an unperceiving substance, then surely it follows that no shape or mode of extension [= ‘or specific way of being extended’] that we can have any idea of—in perceiving or imagining—can be really inherent in matter. Whether the sensible quality is shape or sound or colour or what you will, it seems impossible that any of these should subsist in something that doesn’t perceive it. (Not to mention the peculiar difficulty there must be in conceiving a material substance, prior to and distinct from extension, to be the substratum of extension. ·I’ll say more about that shortly·.)

Hyl: I give up on this point, for just now. But I reserve the right to retract my opinion if I later discover that I was led to it by a false step.

Phil: That is a right you can’t be denied. Shapes and extendedness being disposed of, we proceed next to motion. Can a real motion in any external body be at the same time both very swift and very slow?

Hyl: It cannot.

Phil: Isn’t the speed at which a body moves inversely proportional to the time it takes to go any given distance? Thus a body that travels a mile in an hour moves three times as fast as it would if it travelled only a mile in three hours.

Hyl: I agree with you.

Phil: And isn’t time measured by the succession of ideas in our minds?

Hyl: It is.

Phil: And isn’t it possible that ideas should succeed one another twice as fast in your mind as they do in mine, or in the mind of some kind of non-human spirit?

Hyl: I agree about that.

Phil: Consequently the same body may seem to another spirit to make its journey in half the time that it seems to you to take. (Half is just an example; any other fraction would make the point just as well.) That is to say, according to your view that both of the perceived motions are in the object, a single body can really move both very swiftly and very slowly at the same time. How is this consistent either with common sense or with what you recently agreed to?

Hyl: I have nothing to say to it.

Phil: Now for solidity: If you don’t use ‘solidity’ to name any sensible quality, then it is irrelevant to our enquiry. If you do use it to name a sensible quality, the quality must be either hardness or resistance. But each of these is plainly relative to our senses: it is obvious that what seems hard to one animal may appear soft to another that has greater force and firmness of limbs; and it is equally obvious that the resistance I feel ·when I press against a body· is not in the body.

Hyl: I agree that the sensation of resistance, which is all you immediately perceive, is not in the body; but the cause of that sensation is.

Phil: But the causes of our sensations aren’t immediately perceived, and therefore aren’t sensible. I thought we had settled this point.

Hyl: I admit that we did. Excuse me if I seem a little embarrassed; I am having trouble quitting my earlier views.

Phil: It may be a help for you to consider this point: once extendedness is admitted to have no existence outside the mind, the same must be granted for motion, solidity, and gravity, since obviously they all presuppose extendedness. So it is superfluous to enquire into each of them separately; in denying extendedness, you have denied them all to have any real existence.

Hyl: If this is right, Philonous, I wonder why the philosophers who deny the secondary qualities any real existence should yet attribute it to the primary qualities. If there’s no difference between them, how can this be accounted for?

Phil: It isn’t my business to account for every opinion of the philosophers! But there are many possible explanations, one of them being that ·those philosophers were influenced by the fact that· pleasure and pain are associated with the secondary qualities rather than with the primary ones. Heat and cold, tastes and smells, have something more vividly pleasing or disagreeable than what we get from the ideas of extendedness, shape, and motion. And since it is too visibly absurd to hold that pain or pleasure can be in an unperceiving substance, men have more easily been weaned from believing in the external existence of the secondary qualities than of the primary ones. You will see that there is something in this if you recall the distinction you made between moderate heat and intense heat, allowing one a real existence ·outside the mind· while denying it to the other. But after all, there is no rational basis for that distinction; for surely a sensation that is neither pleasing nor painful is just as much a sensation as one that is pleasing or painful; so neither kind should be supposed to exist in an unthinking subject.

Hyl: It has just come into my head, Philonous, that I have somewhere heard of a distinction between absolute and sensible extendedness. Granted that large and small consist merely in the relation other extended things have to the parts of our own bodies, and so aren’t really in the substances themselves; still, we don’t have to say the same about absolute extendedness, which is something abstracted from large and small, from this or that particular size and shape. Similarly with motion: fast and slow are altogether relative to the succession of ideas in our own minds. But just because those special cases of motion do not exist outside the mind, it doesn’t follow that the same is true of the absolute motion that is abstracted from them.

Phil: What distinguishes one instance of motion, or of extendedness, from another? Isn’t it something •sensible—for instance some speed, or some size and shape?

Hyl: I think so.

Phil: So these qualities—·namely, absolute motion and absolute extendedness·—which are stripped of all •sensible properties, have no features making them more specific in any way.

Hyl: That is right.

Phil: That is to say, they are extendedness in general, and motion in general.

Hyl: If you say so.

Phil: But everyone accepts the maxim that every thing that exists is particular. How then can motion in general, or extendedness in general, exist in any corporeal substance?

Hyl: I will need time to think about that.

Phil: I think the point can be speedily decided. Without doubt you can tell whether you are able to form this or that idea in your mind. Now I’m willing to let our present dispute be settled in the following way. If you can form in your thoughts a distinct abstract idea of motion or extendedness, having none of those sensible qualities—swift and slow, large and small, round and square, and the like—which we agree exist only in the mind, then I’ll capitulate. But if you can’t, it will be unreasonable for you to insist any longer on something of which you have no notion.

Hyl: To be frank, I cannot.

Phil: Can you even separate the ideas of extendedness and motion from the ideas of all the so-called secondary qualities?

Hyl: What! isn’t it easy to consider extendedness and motion by themselves, abstracted from all other sensible qualities? Isn’t that how the mathematicians handle them?

Phil: I acknowledge, Hylas, that it is not difficult to form general propositions and reasonings about extendedness and motion, without mentioning any other qualities, and in that sense to treat them abstractedly. I can pronounce the word ‘motion’ by itself, but how does it follow from this that I can form in my mind the idea of motion without an idea of body? Theorems about extension and shapes can be proved without any mention of large or small or any other sensible quality, but how does it follow from this that the mind can form and grasp an abstract idea of extension, without any particular size or shape or ·other· sensible quality? Mathematicians study quantity, disregarding any other sensible qualities that go with it on the grounds that they are irrelevant to the proofs. But when they lay aside the words and contemplate the bare ideas, I think you’ll find that they aren’t the pure abstracted ideas of extendedness.

Hyl: But what do you say about pure intellect? Can’t abstracted ideas be formed by that faculty?

Phil: Since I can’t form abstract ideas at all, it is clearly impossible for me to form them with help from ‘pure intellect’, whatever faculty you mean that phrase to refer to. Setting aside questions about the nature of pure intellect and its spiritual objects such as virtue, reason, God, etc., I can say this much that seems clearly true: sensible things can only be perceived by the senses or represented by the imagination; so shape and size don’t belong to pure intellect because they are initially perceived through the senses. If you want to be surer about this, try and see if you can frame the idea of any shape, abstracted from all particularities of size and from other sensible qualities.

Hyl: Let me think a little—I don’t find that I can.

Phil: Well, can you think it possible that something might really exist in nature when it implies a contradiction in its conception?

Hyl: By no means.

Phil: Therefore, since even the mind can’t possibly separate the ideas of •extendedness and motion from •all other sensible qualities, doesn’t it follow that where •the former exist •the latter must also exist?

Hyl: It would seem so.

Phil: Consequently the very same arguments that you agreed to be decisive against the •secondary qualities need no extra help to count just as strongly against the •primary qualities also. Besides, if you trust your senses don’t they convince you that all sensible qualities co-exist, that is, that they all appear to the senses as being in the same place? Do your senses ever represent a motion or shape as being divested of all other visible and tangible qualities?

Hyl: You needn’t say any more about this. I freely admit— unless there has been some hidden error or oversight in our discussion up to here—that all sensible qualities should alike be denied existence outside the mind. But I fear that I may have been too free in my former concessions, or overlooked some fallacy in your line of argument. In short, I didn’t take time to think.

Phil: As to that, Hylas, take all the time you want to go back over our discussion. You are at liberty to repair any slips you have made, or to support your initial opinion by presenting arguments that you have so far overlooked.

Hyl: I think it was a big oversight on my part that I failed to distinguish sufficiently the object from the sensation. The sensation cannot exist outside the mind, but it doesn’t follow that the object cannot either.

Phil: What object do you mean? The object of the senses?

Hyl: Exactly.

Phil: So it is immediately perceived?

Hyl: Right. Phil: Explain to me the difference between what is immediately perceived and a sensation.

Hyl: I take the sensation to be an act of the perceiving mind; beside which, there is something perceived, which I call the object ·of the act·. For example, there is red and yellow on that tulip, but the act of perceiving those colours is in me only, and not in the tulip.

Phil: What tulip are you talking about? Is it the one that you see?

Hyl: The same.

Phil: And what do you see beside colour, shape, and extendedness?

Hyl: Nothing.

Phil: So you would say that the red and yellow are coexistent with the extension, wouldn’t you?

Hyl: ·Yes, and· I go further: I say that they have a real existence outside the mind in some unthinking substance.

Phil: That the colours are really in the tulip which I see, is obvious. Nor can it be denied that this tulip may exist independently of your mind or mine; but that any immediate object of the senses—that is, any idea or combination of ideas—should exist in an unthinking substance, or exterior to all minds, is in itself an obvious contradiction. Nor can I imagine how it follows from what you said just now, namely that the red and yellow are in the tulip you saw, since you don’t claim to see that unthinking substance.

Hyl: You are skillful at changing the subject, Philonous.

Phil: I see that you don’t want me to push on in that direction. So let’s return to your distinction between sensation and object. If I understand you correctly, you hold that in every perception there are two things of which one is an action of the mind and the other is not.

Hyl: True.

Phil: And this action can’t exist in or belong to any unthinking thing; but whatever else is involved in a perception may do so.

Hyl: That is my position.

Phil: So that if there were a perception without any act of the mind, that perception could exist in an unthinking substance.

Hyl: I grant that. But it is impossible that there should be such a perception.

Phil: When is the mind said to be active?

Hyl: When it produces, puts an end to, or changes anything.

Phil: Can the mind produce, discontinue, or change anything in any way except by an •act of the will?

Hyl: It cannot.

Phil: So the mind is to count as being active in its perceptions to the extent that •volition is included in them.

Hyl: It is.

Phil: When I •pluck this flower I am active, because I do it by a hand-movement which arose from my volition; so likewise in •holding it up to my nose. But is either of these smelling?

Hyl: No.

Phil: I also act when I draw air through my nose, because my breathing in that manner rather than otherwise is an effect of my volition. But this isn’t smelling either; for if it were, I would smell every time I breathed in that manner.

Hyl: True.

Phil: Smelling, then, is a result of all this ·plucking, holding up, and breathing in·.

Hyl: It is.

Phil: But I don’t find that my will is involved any further— ·that is, in anything other than the plucking, holding up, and breathing in·. Whatever else happens—including my perceiving a smell—is independent of my will, and I am wholly passive with respect to it. Is it different in your case, Hylas?

Hyl: No, it’s just the same.

Phil: Now consider seeing: isn’t it in your power to open your eyes or keep them shut, to turn them this way or that?

Hyl: Without doubt.

Phil: But does it similarly depend on your will that when you look at this flower you perceive white rather than some other colour? When you direct your open eyes towards that part of the sky, can you avoid seeing the sun? Or is light or darkness the effect of your volition?

Hyl: No, certainly.

Phil: In these respects, then, you are altogether passive.

Hyl: I am.

Phil: Tell me now, does seeing consist •in perceiving light and colours or rather in •opening and turning the eyes?

Hyl: The former, certainly.

Phil: Well, then, since in the actual perception of light and colours you are altogether passive, what has become of that action that you said was an ingredient in every sensation? And doesn’t it follow from your own concessions that the perception of light and colours—which doesn’t involve any action—can exist in an unperceiving substance? And isn’t this a plain contradiction?

Hyl: I don’t know what to think.

Phil: Furthermore, since you distinguish active and passive elements in every perception, you must do it in the perception of pain. But how could pain—however inactive it is—possibly exist in an unperceiving substance? Think about it, and then tell me frankly: aren’t light and colours, tastes, sounds, etc. all equally passions or sensations in the mind? You may call them ‘external objects’, and give them in words whatever kind of existence you like; but examine your own thoughts and then tell me whether I am not right?

Hyl: I admit, Philonous, that when I look carefully at •what goes on in my mind, all I can find is that I am a thinking being that has a variety of sensations; and I can’t conceive how a sensation could exist in an unperceiving substance. But when on the other hand I look in a different way at •sensible things, considering them as so many properties and qualities, I find that I have to suppose a material substratum, without which they can’t be conceived to exist.

Phil: Material substratum you call it? Tell me, please, which of your senses acquainted you with it?

Hyl: It is not itself sensible; only its properties and qualities are perceived by the senses.

Phil: I presume, then, that you obtained the idea of it through reflection and reason.

Hyl: I don’t claim to have any proper •positive idea of it. [Here ‘positive’ means ‘non-relational’: Hylas means that he doesn’t have an idea that represents what material substance is like in itself.] But I conclude that it exists, because qualities can’t be conceived to exist without a support.

Phil: So it seems that you have only a •relative notion of material substance: you conceive it only by conceiving how it relates to sensible qualities.

Hyl: Right.

Phil: Tell me, please, what that relation is.

Hyl: Isn’t it sufficiently expressed in the term ‘substratum’ or ‘substance’? [One is Latin, and means ‘underneath layer’; the other comes from Latin meaning ‘standing under’.]

Phil: If so, the word ‘substratum’ should mean that it is spread under the sensible qualities.

Hyl: True.

Phil: And consequently ·spread· under extendedness.

Hyl: I agree.

Phil: So in its own nature it is entirely distinct from extendedness.

Hyl: I tell you, extendedness is only a quality, and matter is something that supports qualities. And isn’t it obvious that the supported thing is different from the supporting one?

Phil: So something distinct from extendedness, and not including it, is supposed to be the substratum of extendedness.

Hyl: Just so.

Phil: Tell me, Hylas, can a thing be spread without being extended? Isn’t the idea of extendedness necessarily included in ·that of· spreading?

Hyl: It is.

Phil: So anything that you suppose to be spread under something else must have in itself an extendedness distinct from the extendedness of the thing under which it is spread.

Hyl: It must.

Phil: Consequently every bodily substance, being the substratum of extendedness, must have in itself another extendedness which qualifies it to be a substratum, ·and that extendedness must also have something spread under it, a sub-substratum, so to speak·, and so on to infinity. Isn’t this absurd in itself, as well as conflicting with what you have just said, namely that the substratum was something distinct from extendedness and not including it?

Hyl: Yes, but Philonous you misunderstand me. I don’t mean that matter is ‘spread’ in a crude literal sense under extension. The word ‘substratum’ is used only to express in general the same thing as ‘substance’.

Phil: Well, then, let us examine the relation implied in the term ‘substance’. Is it not the relation of standing under qualities?

Hyl: The very same.

Phil: But doesn’t a thing have to be extended if it is to stand under or support another?

Hyl: Yes.

Phil: So isn’t this supposition infected with the same absurdity as the previous one?

Hyl: You still take things in a strict literal sense; that isn’t fair, Philonous.

Phil: I don’t want to force any meaning onto your words; you are free to explain them as you please. But please make me understand something by them! You tell me that matter supports or stands under accidents. How? As your legs support your body?

Hyl: No; that is the literal sense.

Phil: Please let me know any sense, literal or not literal, that you understand it in.—How long must I wait for an answer, Hylas?

Hyl: I don’t know what to say. I once thought I understood well enough what was meant by matter’s ‘supporting’ qualities. But now the more I think about it the less I understand it. In short, I find that I don’t know anything about it.

Phil: So it seems that you have no idea at all, either positive or relative, of matter. You don’t know what it is in itself, or what relation it has to qualities.

Hyl: I admit it.

Phil: And yet you said that you couldn’t conceive the real existence of qualities without conceiving at the same time a material support for them.

Hyl: I did.

Phil: That amounted to saying that when you conceive the real existence of qualities you also conceive something that you can’t conceive!

Hyl: It was wrong, I admit. But still I fear there is some fallacy or other. Let me try this: It has just occurred to me that we were both led into error by your treating each quality by itself. I grant that no quality can exist on its own outside the mind; colour can’t exist without extension, nor can shape exist without some other sensible quality. But as a number of qualities united or blended together constitute an entire sensible thing, there is no obstacle to supposing that such things—·that is, such collections of qualities·—can exist outside the mind.

Phil: Are you joking, Hylas, or do you have a very bad memory? We did indeed go through all the qualities by name, one after another; but my arguments—or rather your concessions—nowhere tended to prove that the secondary qualities don’t exist ·outside the mind· in isolation; the point was rather that secondary qualities don’t exist ·outside the mind· at all. ·It’s true that existing-in-isolation did come up in our discussion·: in discussing shape and motion, we concluded they couldn’t exist outside the mind because it was impossible even in thought to separate them from all secondary qualities, so as to conceive them existing by themselves. But this wasn’t the only argument I used on that occasion. However, if you like we can set aside our whole conversation up to here, counting it as nothing. I am willing to let our whole debate be settled as follows: If you can conceive it to be possible for any mixture or combination of qualities, or any sensible object whatever, to exist outside the mind, then I will grant it actually to be so.

Hyl: By that test, the point will soon be decided. What is easier than to conceive a tree or house existing by itself, independently of and unperceived by any mind whatsoever? I conceive them existing in that way right now.

Phil: Tell me, Hylas, can you see a thing which is at the same time unseen?

Hyl: No, that would be a contradiction.

Phil: Is it not as great a contradiction to talk of conceiving a thing which is unconceived?

Hyl: It is.

Phil: The tree or house therefore which you think of is conceived by you.

Hyl: How could it be otherwise?

Phil: And what is conceived is surely in the mind.

Hyl: Without question, what is conceived is in the mind.

Phil: Then what led you to say that you conceived a house or tree existing independently and out of all minds whatsoever?

Hyl: That was an oversight, I admit; but give me a moment to think about what led me into it. It was—·I now realize, after reflection·—an amusing mistake. As I was thinking of a tree in a solitary place with nobody there to see it, I thought that was conceiving a tree as existing unperceived or unthought of, overlooking the fact I myself conceived it all the while. But now I plainly see that all I can do is to form ideas in my own mind. I can conceive in my own thoughts the idea of a tree, or a house, or a mountain, but that is all. And this is far from proving that I can conceive them existing out of the minds of all spirits.

Phil: You agree, then, that you can’t conceive how any corporeal sensible thing should exist otherwise than in a mind.

Hyl: I do.

Phil: And yet you will earnestly contend for the truth of something that you can’t even conceive.

Hyl: I admit that I don’t know what to think, but I still have doubts. Isn’t it certain that I see things at a distance? Don’t we perceive the stars and moon, for example, to be a long way away? Isn’t this, I say, obvious to the senses?

Phil: Don’t you in dreams also perceive objects like those?

Hyl: I do.

Phil: And don’t they then appear in the same way to be distant?

Hyl: They do.

Phil: But do you conclude that the apparitions in a dream are outside the mind?

Hyl: By no means.

Phil: Then you ought not to conclude that sensible objects ·seen when you are awake· are outside the mind, from their appearance or the manner in which you perceive them.

Hyl: I admit that. But doesn’t my ·visual· sense deceive me in those cases, ·by telling me that sensible objects are at a distance when really they are not·?

Phil: By no means. Neither eyesight nor reason inform you that the idea or thing that you immediately perceive actually exists outside the mind. By eyesight you know only that you are affected with certain sensations of light and colours, etc. And you won’t say that these are outside the mind.

Hyl: True; but all the same, don’t you think that eyesight makes some suggestion of outerness or distance?

Phil: When you approach a distant object, do the visible size and shape keep changing, or do they appear the same at all distances?

Hyl: They are in a continual change.

Phil: So sight doesn’t ‘suggest’ or in any way inform you that the visible object you immediately perceive exists at a distance, or that it will be perceived when you move further forward; because there is a continued series of visible objects succeeding each other during the whole time of your approach.

Hyl: I agree about that: but still I know, on seeing an object, what object I shall see after I have gone a certain distance—never mind whether it is exactly the same object or not. So something about distance is still being suggested.

Phil: My dear Hylas, just think about that a little, and then tell me whether there is anything more to it that this: From the ideas that you actually perceive by sight you have by experience learned to infer (in accordance with the general rules of nature) what other ideas you will experience after such and such a succession of time and motion.

Hyl: Upon the whole, I think that’s what it comes down to.

Phil: Isn’t it obvious that if a man born blind were suddenly enabled to see, he would start with no experience of what may be suggested by sight?

Hyl: It is.

Phil: So he would not, according to you, have any notion of distance linked to the things he saw. He would take the latter to be a new set of sensations existing only in his mind.

Hyl: That is undeniable.

Phil: But to make it still more plain: isn’t distance a line running out from the eye?

Hyl: It is.

Phil: Can a line so situated be perceived by sight?

Hyl: It cannot.

Phil: So doesn’t it follow that distance isn’t strictly and immediately perceived by sight?

Hyl: It seems so.

Phil: Again, do you think that colours are at a distance?

Hyl: I have to acknowledge that they are only in the mind.

Phil: But don’t colours appear to the eye as coexisting at the same place as extension and shape

Hyl: They do.

Phil: Then how can you conclude from ·the deliverances of· sight that shapes •do exist outside the mind, when you agree that colours •don’t? The sensible appearances of both are the very same.

Hyl: I don’t know what to answer.

Phil: Even if distance were truly and immediately perceived by the mind, it still wouldn’t follow that it existed out of the mind. For whatever is immediately perceived is an idea; and can any idea exist out of the mind?

Hyl: It would be absurd to suppose so. But tell me, Philonous, can we perceive or know nothing except our ideas?

Phil: Set aside ·what we may know through· the rational deducing of causes from effects; that is irrelevant to our enquiry. As for the senses: you are the best judge of whether you •perceive anything that you don’t •immediately perceive. And I ask you, are the things you immediately perceive anything but your own sensations or ideas? In the course of this conversation you have more than once declared yourself on those two points; this latest question of yours seems to indicate that you have changed your mind.

Hyl: To tell you the truth, Philonous, I think there are two kinds of objects: one kind perceived immediately, and called ‘ideas’; the other kind are real things or external objects perceived by the mediation of ideas, which resemble and represent them. Now I grant that ideas don’t exist outside the mind; but the second sort of objects do. I am sorry I didn’t think of this distinction sooner; it would probably have cut short your discourse.

Phil: Are those external objects perceived by •sense, or by •some other faculty?

Hyl: They are perceived by sense.

Phil: What? Is there anything perceived by sense that isn’t immediately perceived?

Hyl: Yes, Philonous, there is—in a way. For example, when I look at a picture or statue of Julius Caesar, I may be said to perceive him in a fashion (though not immediately) by my senses.

Phil: You seem to hold, then, that our ideas, which are all that we immediately perceive, are pictures of external things; and that the latter are also perceived by sense because they have a conformity or resemblance to our ideas.

Hyl: That is my meaning.

Phil: And in the same way that Julius Caesar, in himself invisible, is nevertheless perceived by sight, so also real things, in themselves imperceptible, are perceived by sense.

Hyl: In the very same way.

Phil: Tell me, Hylas, when you look at the picture of Julius Caesar, do you see with your eyes anything more than some colours and shapes, with a certain symmetry and composition of the whole?

Hyl: Nothing else.

Phil: And wouldn’t a man who had never known anything about Julius Caesar see as much?

Hyl: He would.

Phil: So he has his sight, and the use of it, as perfectly as you have yours.

Hyl: I agree with you.

Phil: Then why are your thoughts directed to the Roman emperor while his are not? This can’t come from the sensations or ideas of sense that you perceive at that moment, for you have agreed that you have in that respect no advantage over the man who has never heard of Julius Caesar. So it seems that the direction of your thoughts comes from reason and memory—doesn’t it?

Hyl: It does.

Phil: So that example of yours doesn’t show that anything is perceived by sense that isn’t immediately perceived. I don’t deny that we can be said in a certain sense to perceive sensible things mediately by sense: that is when the immediate perception of ideas by one sense suggests to the mind others, perhaps belonging to another sense, of a kind that have often been perceived to go with ideas of the former kind. For instance, when I hear a coach drive along the streets, all that I immediately perceive is the sound; but from my past experience that such a sound is connected with a coach, I am said to ‘hear the coach’. Still, it is obvious that in truth and strictness nothing can be heard but sound; and the coach in that example is not strictly perceived by sense but only suggested from experience. Similarly, when we are said to see a red-hot bar of iron; the solidity and heat of the iron are not the objects of sight, but are suggested to the imagination by the colour and shape that are strictly perceived by that sense. In short,

the only things that are actually and strictly perceived by any sense are the ones that would have been perceived even if we had only just acquired that sense ·and were using it for the first time·.

As for other things, clearly they are only suggested to the mind by past experience. But to return to your comparison of ·imperceptible ‘real things’ with· Caesar’s picture: obviously, if you keep to this you’ll have to hold that the real things that our ideas copy are perceived not by sense but by some internal faculty of the soul such as •reason or •memory. I would be interested to know what arguments •reason gives you for the existence of your ‘real things’ or material objects; or whether you •remember seeing them formerly ·not as copied by your ideas but· as they are in themselves; or if you have heard or read of anyone else who did!

Hyl: I can see that you want to make fun of me, Philonous; but that will never convince me.

Phil: All I want is to learn from you how to come by knowledge of material things. Whatever we perceive is perceived either immediately by sense, or mediately by reason and reflection. But you have excluded sense; so please show me what reason you have to believe in their existence, or what means you can possibly adopt to prove, to my understanding or your own, that they exist.

Hyl: To be perfectly frank, Philonous, now that I think about it I can’t find any good reason for my position. But it seems pretty clear that it’s at least possible that such things really exist; and as long as there is no absurdity in supposing them, I shall continue in my belief until you bring good reasons to the contrary.

Phil: What? Has it come to this, that you believe in the existence of material objects, and that this belief is based on the mere possibility of its being true? Then you challenge me to bring reasons against it; though some people would think that the burden of proof lies with him who holds the affirmative position. Anyway, this very thesis that you are now determined to maintain without any reason is in effect one that you have—more than once during this conversation—seen good reason to give up. But let us set all that aside. If I understand you rightly, you say our ideas don’t exist outside the mind, but that they are copies, likenesses, or representations of certain originals that do.

Hyl: You have me right.

Phil: Our ideas, then, are like external things.

Hyl: They are.

Phil: Do those external things have a stable and permanent nature independently of our senses; or do they keep changing as we move our bodies and do things with our faculties or organs of sense?

Hyl: Real things, obviously, have a fixed and real nature which remains the same through any changes in our senses or in how our bodies are placed or how they move. Such changes may indeed affect the ideas in our minds, but it would be absurd to think they had the same effect on things existing outside the mind. Phil: How, then, can things that are perpetually fleeting and variable as our ideas are be copies or likenesses of any thing that is fixed and constant? Since all sensible qualities—size, shape, colour, etc.—that is, our ideas, are continually changing with every alteration in the distance, medium, or instruments of sensation, how can any fixed material object be properly represented or depicted by several distinct things ·or ideas·, each of which is so unlike the others? Or if you say that the object resembles just one of our ideas, how can we distinguish that true copy from all the false ones?

Hyl: I have to admit, Philonous, that I am at a loss. I don’t know what to say to this.

Phil: There is more. Are material objects in themselves perceptible or imperceptible?

Hyl: Properly and immediately nothing can be perceived but ideas. All material things, therefore, are in themselves insensible, and can be perceived only through ideas of them.

Phil: Ideas are sensible, then, and their originals—the things they are copies of—are insensible?

Hyl: Right.

Phil: But how can something that is sensible be like something that is insensible? Can a real thing, in itself invisible, be like a colour? Can a real thing that isn’t audible be like a sound? In a word, can anything be like a sensation or idea but another sensation or idea?

Hyl: I must admit that I think not.

Phil: Can there possibly be any doubt about this? Don’t you perfectly know your own ideas?

Hyl: Yes, I know them perfectly; for something that I don’t perceive or know can’t be any part of my idea.

Phil: Well, then, examine your ideas, and then tell me if there’s anything in them that could exist outside the mind, or if you can conceive anything like them existing outside the mind.

Hyl: Upon looking into it I find that I can’t conceive or understand how anything but an idea can be like an idea. And it is most evident that no idea can exist outside the mind.

Phil: So you’re forced by your own principles to deny the reality of sensible things, because you made it consist in an absolute existence outside the mind. That is to say, you are a downright sceptic. So I have met my target, which was to show that your principles lead to scepticism.

Hyl: For the present I am, if not entirely convinced, at least silenced.

Phil: I wonder what more you would require in order to be perfectly convinced. Haven’t you been free to explain yourself in any way you liked? Were any little conversational slips held against you? Weren’t you allowed to retract or reinforce anything you had previously said, as best served your purpose? Hasn’t everything you could say been heard and examined with all the fairness imaginable? In a word, haven’t you on every point been convinced out of your own mouth? And if you can now discover any flaw in any of your former concessions, or think of any remaining tactic, any new distinction, shading, or comment whatsoever, why don’t you produce it?

Hyl: A little patience, Philonous. I am at present so bewildered to see myself entangled, and as it were imprisoned in the labyrinths you have led me into, that I can’t be expected to find my way out on the spur of the moment. You must give me time to look around me, and recollect myself.

Phil: Listen—isn’t that the college-bell? Let us go in, and meet here again tomorrow morning. In the mean time you can think about this morning’s conversation, and see if you can find any fallacy in it, or invent any new means to extricate yourself.

Hyl: Agreed.