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.