THAT when a thing lies still,unless somewhat else stir it,it will lie still for ever,is a truth that no man doubts of.But that when a thing is in motion,it will eternally be in motion,unless somewhat else stay it,though the reason be the same (namely,that nothing can change itself),is not so easily assented to.For men measure,not only other men,but all other things,by themselves:
and because they find themselves subject after motion to pain and lassitude,think everything else grows weary of motion,and seeks repose of its own accord;little considering whether it be not some other motion wherein that desire of rest they find in themselves consisteth.From hence it is that the schools say,heavy bodies fall downwards out of an appetite to rest,and to conserve their nature in that place which is most proper for them;ascribing appetite,and knowledge of what is good for their conservation (which is more than man has),to things inanimate,absurdly.
When a body is once in motion,it moveth (unless something else hinder it)eternally;and whatsoever hindreth it,cannot in an instant,but in time,and by degrees,quite extinguish it:and as we see in the water,though the wind cease,the waves give not over rolling for a long time after;so also it happeneth in that motion which is made in the internal parts of a man,then,when he sees,dreams,etc.For after the object is removed,or the eye shut,we still retain an image of the thing seen,though more obscure than when we see it.And this is it the Latins call imagination,from the image made in seeing,and apply the same,though improperly,to all the other senses.But the Greeks call it fancy,which signifies appearance,and is as proper to one sense as to another.
Imagination,therefore,is nothing but decaying sense;and is found in men and many other living creatures,as well sleeping as waking.
The decay of sense in men waking is not the decay of the motion made in sense,but an obscuring of it,in such manner as the light of the sun obscureth the light of the stars;which stars do no less exercise their virtue by which they are visible in the day than in the night.But because amongst many strokes which our eyes,ears,and other organs receive from external bodies,the predominant only is sensible;therefore the light of the sun being predominant,we are not affected with the action of the stars.And any object being removed from our eyes,though the impression it made in us remain,yet other objects more present succeeding,and working on us,the imagination of the past is obscured and made weak,as the voice of a man is in the noise of the day.From whence it followeth that the longer the time is,after the sight or sense of any object,the weaker is the imagination.For the continual change of man's body destroys in time the parts which in sense were moved:so that distance of time,and of place,hath one and the same effect in us.For as at a great distance of place that which we look at appears dim,and without distinction of the smaller parts,and as voices grow weak and inarticulate:so also after great distance of time our imagination of the past is weak;and we lose,for example,of cities we have seen,many particular streets;and of actions,many particular circumstances.This decaying sense,when we would express the thing itself (I mean fancy itself),we call imagination,as I said before.
But when we would express the decay,and signify that the sense is fading,old,and past,it is called memory.So that imagination and memory are but one thing,which for diverse considerations hath diverse names.
Much memory,or memory of many things,is called experience.
Again,imagination being only of those things which have been formerly perceived by sense,either all at once,or by parts at several times;the former (which is the imagining the whole object,as it was presented to the sense)is simple imagination,as when one imagineth a man,or horse,which he hath seen before.The other is compounded,when from the sight of a man at one time,and of a horse at another,we conceive in our mind a centaur.So when a man compoundeth the image of his own person with the image of the actions of another man,as when a man imagines himself a Hercules or an Alexander (which happeneth often to them that are much taken with reading of romances),it is a compound imagination,and properly but a fiction of the mind.There be also other imaginations that rise in men,though waking,from the great impression made in sense:as from gazing upon the sun,the impression leaves an image of the sun before our eyes a long time after;and from being long and vehemently attent upon geometrical figures,a man shall in the dark,though awake,have the images of lines and angles before his eyes;which kind of fancy hath no particular name,as being a thing that doth not commonly fall into men's discourse.