CHAPTER II.

2. Definition of sense. 4. Four propositions concerning the nature of conceptions. 5. The first proved. 6. The second proved. 7, 8. The third proved. 9. The fourth proved. 10. The main deception of sense.

1. Having declared what I mean by the word _conception_, and other words equivalent thereunto, I come to the _conceptions_ themselves, to shew their _differences_, their _causes_, and the _manner of the production_, so far as is necessary for this place.

[Sidenote: Definition of sense.]

2. Originally all _conceptions_ proceed from the _action_ of the thing itself, whereof it is the conception: now when the action is _present_, the conception it produceth is also called _sense_; and the thing by whose action the same is produced, is called the _object of the sense_.

3. By our several _organs_ we have several _conceptions_ of several qualities in the objects; for by _sight_ we have a conception or image composed of _colour_ and _figure_, which is all the notice and knowledge the object imparteth to us of its nature by the eye. By _hearing_ we have a conception called _sound_, which is all the knowledge we have of the quality of the object from the ear. And so the rest of the senses are also conceptions of several qualities, or natures of their objects.

[Sidenote: Four propositions concerning the nature of conceptions.]

4. Because the _image_ in vision consisting of _colour_ and _shape_ is the knowledge we have of the qualities of the object of that sense; it is no hard matter for a man to fall into this opinion, that the same _colour_ and _shape_ are the _very qualities themselves_; and for the same cause, that _sound_ and _noise_ are the _qualities of the bell_, or of the air. And this opinion hath been so long received, that the _contrary_ must needs appear a great paradox; and yet the introduction of _species visible_ and _intelligible_ (which is necessary for the maintenance of that opinion) passing to and fro from the _object_, is _worse_ than any paradox, as being a plain _impossibility_. I shall therefore endeavour to make plain these points:

That the subject wherein colour and image are inherent, is _not_ the _object_ or thing seen.

That there is nothing _without us_ (really) which we call an _image_ or colour.

That the said image or colour is but an _apparition_ unto us of the _motion_, agitation, or alteration, which the _object_ worketh in the _brain_, or spirits, or some internal substance of the head.

That as in _vision_, so also in conceptions that arise from the _other senses_, the subject of their _inherence_ is not the _object_, but the _sentient_.

[Sidenote: The first proved]

5. Every man hath so much experience as to have seen the _sun_ and the other visible objects by reflection in the _water_ and _glasses_; and this alone is sufficient for this conclusion, that _colour_ and _image_ may be there where the _thing seen_ is _not_. But because it may be said that notwithstanding the _image_ in the water be not in the object, but a thing merely _phantastical_, yet there may be _colour_ really in the thing itself: I will urge further this experience, that divers times men see directly the _same_ object _double_, as _two candles_ for _one_, which may happen from distemper, or otherwise without distemper if a man will, the organs being either in their right temper, or equally distempered; the _colours_ and _figures_ in two such images of the same thing _cannot be inherent_ therein, because the thing seen cannot be in _two places_.

_One_ of these images therefore is _not inherent_ in the object: but seeing the organs of the sight are then in equal temper or distemper, the _one_ of them is no more inherent than the _other_; and consequently _neither_ of them both are in the object; which is the first proposition, mentioned in the precedent number.

[Sidenote: The second proved.]

6. Secondly, that the image of any thing by _reflection_ in a _glass_ or _water_ or the like, is _not_ any thing _in_ or _behind_ the glass, or _in_ or _under_ the water, every man may grant to himself; which is the second proposition.

[Sidenote: The third proved.]

7. For the third, we are to consider, first that upon every _great agitation_ or _concussion_ of the _brain_ (as it happeneth from a stroke, especially if the stroke be upon the eye) whereby the optic nerve suffereth any great violence, there _appeareth_ before the _eyes_ a certain light, which light is _nothing without_, but an apparition only, all that is real being the concussion or motion of the parts of that nerve; from which experience we may conclude, that _apparition of light is really nothing but motion_ within. If therefore from _lucid bodies_ there can be derived _motion_, so as to affect the optic nerve in such manner as is proper thereunto, there will follow an _image_ of light somewhere in that line by which the motion was last derived to the eye; that is to say, in the object, if we look directly on it, and in the glass or water, when we look upon it in the line of reflection, which in effect is the third proposition; namely, that image and colour is but an apparition to us of that motion, agitation, or alteration which the object worketh in the brain or spirits, or some _internal_ substance in the head.

8. But that _from all lucid_, shining and illuminate bodies, there is a _motion produced_ to the eye, and, through the eye, to the _optic_ nerve, and so into the _brain_, by which that apparition of _light_ or _colour_ is affected, is not hard to prove. And first, it is evident that the _fire_, the only lucid body here upon earth, worketh by _motion_ equally every way; insomuch as the motion thereof _stopped_ or inclosed, it is presently _extinguished_, and no more fire. And further, that that motion, whereby the fire worketh, is _dilation_, and _contraction_ of itself _alternately_, commonly called _scintillation_ or glowing, is manifest also by experience. From such _motion_ in the fire must needs arise a _rejection_ or casting from itself of that part of the _medium_ which is _contiguous_ to it, whereby that part also rejecteth the _next_, and so successively one part beateth back another to the very _eye_; and in the same manner the _exterior_ part of the eye presseth the _interior_, (the laws of refraction still observed). Now the interior coat of the eye is nothing else but a piece of the _optic_ nerve; and therefore the motion is still continued thereby into the _brain_, and by _resistance_ or reaction of the brain, is also a _rebound_ into the optic nerve again; which we _not conceiving_ as motion or rebound from _within_, do think it is _without_, and call it _light_; as hath been already shewed by the experience of a stroke. We have no reason to doubt, that the fountain of light, the _sun_, worketh by any other ways than the _fire_, at least in this matter. And thus all _vision_ hath its original from such _motion_ as is here described: for where there is no light, there is no sight; and therefore _colour_ also must be the same thing with _light_, as being the effect of the lucid bodies: their _difference_ being only this, that when the light cometh _directly_ from the fountain to the eye, or _indirectly_ by reflection from _clean_ and _polite_ bodies, and such as have _not_ any particular motion internal to alter it, we call it _light_; but when it cometh to the eye by reflection from _uneven_, _rough_, and coarse bodies, or such as are affected with internal motion of their own that may alter it, then we call it _colour_; colour and light differing only in this, that the one is _pure_, and the other _perturbed_ light. By that which hath been said, not only the truth of the third proposition, but also the whole manner of producing light and colour, is apparent.

[Sidenote: The fourth proved.]

9. As colour is not inherent in the object, but an effect thereof upon us, caused by such motion in the object, as hath been described: so neither is _sound_ in the thing we hear, but in ourselves. One manifest sign thereof is, that as a man may _see_, so also he may _hear double_ or _treble_, by multiplication of _echoes_, which echoes are sounds as well as the original; and _not_ being in one and the _same place_, cannot be _inherent_ in the body that maketh them. Nothing can make any thing which is not in itself: the _clapper_ hath no _sound_ in it, but _motion_, and maketh motion in the internal parts of the bell; so the _bell_ hath motion, and not sound, that imparteth _motion_ to the _air_; and the _air_ hath motion, but not sound; the _air_ imparteth motion by the _ear_ and _nerve_ unto the _brain_; and the brain hath motion but not sound; from the _brain_, it reboundeth back into the nerves _outward_, and thence it becometh an _apparition without_, which we call _sound_. And to proceed to the _rest_ of the _senses_, it is apparent enough, that the _smell_ and _taste_ of the _same thing_, are _not_ the _same_ to _every man_; and therefore are not in the thing _smelt_ or _tasted_, but in the men. So likewise the _heat_ we feel from the fire is manifestly in _us_, and is quite _different_ from the heat which is in the _fire_: for _our_ heat is _pleasure_ or _pain_, according as it is _great_ or _moderate_; but in the _coal_ there is no such thing. By this the fourth and last proposition is proved, _viz._ that as in vision, so also in conceptions that arise from _other_ senses, the subject of their inherence is not in the object, but in the sentient.

[Sidenote: The main deception of sense.]

10. And from hence also it followeth, that _whatsoever accidents_ or qualities our senses make us think there be in the _world_, they be _not_ there, but are _seeming_ and _apparitions_ only: the things that really _are_ in the world without us, are those _motions_ by which these seemings are caused. And this is the _great deception of sense_, which also is to be by sense _corrected_: for as sense telleth me, when I see _directly_, that the colour seemeth to _be_ in the object; so also sense telleth me, when I see by _reflection_, that colour is not in the object.

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