_Phil._ Tell me, Hylas, to which of the senses, think you, the idea of motion belongs? to the hearing?
_Hyl._ No, certainly; but to the sight and touch.
_Phil._ It should follow then, that, according to you, real sounds may possibly be _seen_ or _felt_, but never _heard_.
_Hyl._ Look you, Philonous, you may, if you please, make a jest of my opinion, but that will not alter the truth of things. I own, indeed, the inferences you draw me into sound something oddly; but common language, you know, is framed by, and for the use of the vulgar: we must not therefore wonder if expressions adapted to exact philosophic notions seem uncouth and out of the way.
_Phil._ Is it come to that? I a.s.sure you, I imagine myself to have gained no small point, since you make so light of departing from common phrases and opinions; it being a main part of our inquiry, to examine whose notions are widest of the common road, and most repugnant to the general sense of the world. But, can you think it no more than a philosophical paradox, to say that _real sounds are never heard_, and that the idea of them is obtained by some other sense? And is there nothing in this contrary to nature and the truth of things?
_Hyl._ To deal ingenuously, I do not like it. And, after the concessions already made, I had as well grant that sounds too have no real being without the mind.
_Phil._ And I hope you will make no difficulty to acknowledge the same of _colours_.
_Hyl._ Pardon me: the case of colours is very different. Can anything be plainer than that we see them on the objects?
_Phil._ The objects you speak of are, I suppose, corporeal Substances existing without the mind?
_Hyl._ They are.
_Phil._ And have true and real colours inhering in them?
_Hyl._ Each visible object hath that colour which we see in it.
_Phil._ How! is there anything visible but what we perceive by sight?
_Hyl._ There is not.
_Phil._ And, do we perceive anything by sense which we do not perceive immediately?
_Hyl._ How often must I be obliged to repeat the same thing? I tell you, we do not.
_Phil._ Have patience, good Hylas; and tell me once more, whether there is anything immediately perceived by the senses, except sensible qualities. I know you a.s.serted there was not; but I would now be informed, whether you still persist in the same opinion.
_Hyl._ I do.
_Phil._ Pray, is your corporeal substance either a sensible quality, or made up of sensible qualities?
_Hyl._ What a question that is! who ever thought it was?
_Phil._ My reason for asking was, because in saying, _each visible object hath that colour which we see in it_, you make visible objects to be corporeal substances; which implies either that corporeal substances are sensible qualities, or else that there is something beside sensible qualities perceived by sight: but, as this point was formerly agreed between us, and is still maintained by you, it is a clear consequence, that your _corporeal substance_ is nothing distinct from _sensible qualities_(794).
_Hyl._ You may draw as many absurd consequences as you please, and endeavour to perplex the plainest things; but you shall 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 are unwilling to have your notion of corporeal substance examined, I shall urge that point no farther. Only be pleased to let me know, whether the same colours which we see exist in external bodies, or some other.
_Hyl._ The very same.
_Phil._ What! are then the beautiful red and purple we see on yonder clouds really in them? Or do you imagine they have in themselves any other form than that of a dark mist or vapour?
_Hyl._ I must own, Philonous, those colours are not really in the clouds as they seem to be at this distance. They are only apparent colours.
_Phil._ _Apparent_ call you them? how shall we distinguish these apparent colours from real?
_Hyl._ Very easily. Those are to be thought apparent which, appearing only at a distance, vanish upon a nearer approach.
_Phil._ And those, I suppose, are to be thought real which are discovered by the most near and exact survey.
_Hyl._ Right.
_Phil._ Is the nearest and exactest survey made by the help of a microscope, or by the naked eye?
_Hyl._ By a microscope, doubtless.
_Phil._ But a microscope often discovers colours in an object different from those perceived by the una.s.sisted sight. And, in case we had microscopes magnifying to any a.s.signed degree, it is certain that no object whatsoever, viewed through them, would appear in the same colour which it exhibits to the naked eye.
_Hyl._ And what will you conclude from all this? You cannot argue that there are really and naturally no colours on objects: because by artificial managements they may be altered, or made to vanish.
_Phil._ I think it may evidently be concluded from your own concessions, that all the colours we see with our naked eyes are only apparent as those on the clouds, since they vanish upon a more close and accurate inspection which is afforded us by a microscope. Then, as to what you say by way of prevention: I ask you whether the real and natural state of an object is better discovered by a very sharp and piercing sight, or by one which is less sharp?
_Hyl._ By the former without doubt.
_Phil._ Is it not plain from _Dioptrics_ that microscopes make the sight more penetrating, and represent objects as they would appear to the eye in case it were naturally endowed with a most exquisite sharpness?
_Hyl._ It is.
_Phil._ Consequently the microscopical representation is to be thought that which best sets forth the real nature of the thing, or what it is in itself. The colours, therefore, by it perceived are more genuine and real than those perceived otherwise.
_Hyl._ I confess there is something in what you say.
_Phil._ Besides, it is not only possible but manifest, that there actually are animals whose eyes are by nature framed to perceive those things which by reason of their minuteness escape our sight. What think you of those inconceivably small animals perceived by gla.s.ses? Must we suppose they are all stark blind? Or, in case they see, can it be imagined their sight hath not the same use in preserving their bodies from injuries, which appears in that of all other animals? And if it hath, is it not evident they must see particles less than their own bodies; which will present them with a far different view in each object from that which strikes our senses(795)?
Even our own eyes do not always represent objects to us after the same manner. In the jaundice every one knows that all things seem yellow. Is it not therefore highly probable those animals in whose eyes we discern a very different texture from that of ours, and whose bodies abound with different humours, do not see the same colours in every object that we do?
From all which, should it not seem to follow that all colours are equally apparent, and that none of those which we perceive are really inherent in any outward object?
_Hyl._ It should.
_Phil._ The point will be past all doubt, if you consider that, in case colours were real properties or affections inherent in external bodies, they could admit of no alteration without some change wrought in the very bodies themselves: but, is it not evident from what hath been said that, upon the use of microscopes, upon a change happening in the humours of the eye, or a variation of distance, without any manner of real alteration in the thing itself, the colours of any object are either changed, or totally disappear? Nay, all other circ.u.mstances remaining the same, change but the situation of some objects, and they shall present different colours to the eye. The same thing happens upon viewing an object in various degrees of light. And what is more known than that the same bodies appear differently coloured by candle-light from what they do in the open day? Add to these the experiment of a prism which, separating the heterogeneous rays of light, alters the colour of any object, and will cause the whitest to appear of a deep blue or red to the naked eye. And now tell me whether you are still of opinion that every body hath its true real colour inhering in it; and, if you think it hath, I would fain know farther from you, what certain distance and position of the object, what peculiar texture and formation of the eye, what degree or kind of light is necessary for ascertaining that true colour, and distinguishing it from apparent ones.
_Hyl._ I own myself entirely satisfied, that they are all equally apparent, and that there is no such thing as colour really inhering in external bodies, but that it is altogether in the light. And what confirms me in this opinion is, that in proportion to the light colours are still more or less vivid; and if there be no light, then are there no colours perceived. Besides, allowing there are colours on external objects, yet, how is it possible for us to perceive them? For no external body affects the mind, unless it acts first on our organs of sense. But the only action of bodies is motion; and motion cannot be communicated otherwise than by impulse. A distant object therefore cannot act on the eye; nor consequently make itself or its properties perceivable to the soul. Whence it plainly follows that it is immediately some contiguous substance, which, operating on the eye, occasions a perception of colours: and such is light.
_Phil._ How! is light then a substance?
_Hyl._ I tell you, Philonous, external light is nothing but a thin fluid substance, whose minute particles being agitated with a brisk motion, and in various manners reflected from the different surfaces of outward objects to the eyes, communicate different motions to the optic nerves; which, being propagated to the brain, cause therein various impressions; and these are attended with the sensations of red, blue, yellow, &c.
_Phil._ It seems then the light doth no more than shake the optic nerves.
_Hyl._ Nothing else.
_Phil._ And consequent to each particular motion of the nerves, the mind is affected with a sensation, which is some particular colour.