teration of fome fenfible qualities in thofe fubjects on which they operate, and fo making them exhibit to us new fenfible ideas; therefore it is that I have reckoned these powers amongst the fimple ideas, which make the complex ones of the forts of fubftances; though the fe powers, confidered in themfelves, are truly complex ideas. And in this loofer fenfe I crave leave to be understood, when I name any of thefe potentialities amongst the fimple ideas, which we recollect in our minds, when we think of particular fubftances. For the powers that are feverally in them, are neceflary to be confidered, if we will have true diftinct notions of the feveral forts of fubftances.

§ 8. And why.

NOR are we to wonder, that powers make a great part of our complex ideas of fubfiances, fince their fecondary qualities are thofe, which in moft of them ferve principally to diftinguifh fubftances one from another, and commonly make a confiderable part of the complex idea of the feveral forts of them. For our fenfes failing us in the difcovery of the bulk, texture, and figure of the minute parts of bodies, on which their real conftitutions. and differences depend, we are fain to make ufe of their fecondary qualities as the characteristical notes and marks, whereby to frame ideas of them in our minds, and diftinguish them one from another; all which fecondary qualities, as has been fhown, are nothing but bare powers: For the colour and taste of opium are, as well as its foporific or anodyne virtues, mere powers depending on its primary qualities, whereby it is fitted to produce different operations on different parts of our bodies.

§ 9. Three forts of Ideas make our complex ones of Subftances.

THE Ideas that make our complex ones of corporeal fubftances, are of thefe three forts. Firft, The ideas of the primary qualities of things, which are difcovered by our fenfes, and are in them even when we perceive them not; fuch are the bulk, figure, number, fituation, and motion of the parts of bodies, which are really in

15 them, whether we take notice of them or no. Secondly, The fenfible fecondary qualities, which, depending on thefe, are nothing but the powers thofe fubftances have to produce feveral ideas in us by our fenfes; which ideas are not in the things themselves, otherwife than as any thing is in its caufe. Thirdly, The aptnefs we confider in any fubftance to give or receive fuch alterations of primary qualities, as that the fubftance fo altered should produce in us different ideas from what it did before; thefe are called active and paffive powers: All which powers, as far as we have any notice or notion of them, terminate only in fenfible fimple ideas. For whatever alteration a loadflone has the power to make in the minute particles of iron, we should have no notion of any power it had at all to operate on iron, did not its fenfible motion discover it and I doubt not, but there are a thousand changes, that bodies we daily handle have a power to caufe in one another, which we never fulpect, because they never appear in fenfible effects.

§ 10. Powers make a great part of our complex Ideas of Subftances.

POWERS therefore justly make a great part of our complex ideas of fubftances. He that will examine his complex idea of gold, will find several of its idear that make it up, to be only powers: as the power of being melted, but of not spending itself in the fire; of being diffolved in aq. regia; are ideas as neceffary to make up our complex idea of gold, as its colour and weight which, if duly confidered, are alfo nothing but different powers. For to fpeak truly, yellowness is not actually in gold, but is a power in gold to produce that idea in us by our eyes, when placed in a due light: And the heat, which we cannot leave out of our idea of the fun, is no more really in the fun, than the white colour it introduces into wax. Thefe are both equally powers in the fun, operating, by the motion and figure of its infenfible parts, fo on a man, as to make him have the idea of heat; and fo on wax, as to make it capable to produce in a man the idea of white.

§ 11. The now fecondary Qualities of Bodies would difappear, if we could discover the primary ones of their minute parts.

HAD we fenfes acute enough to difcern the minute particles of bodies, and the real conftitution on which their fenfible qualities depend, I doubt not but they would produce quite different ideas in us; and that which is now the yellow colour of gold would then difappear, and inftead of it we fhould fee an admirable texture of parts of a certain fize and figure. This microscopes plainly difcover to us: For what to our naked eyes produces a certain colour, is, by thus augmenting the acuteness of our fenfes, difcovered to be quite a different thing; and the thus altering, as it were, the proportion of the bulk of the minute parts of a coloured object to our ufual fight, produces different ideas from what it did before. Thus fand or pounded glass, which is opaque, and white to the naked eye, is pellucid in a microscope; and a hair seen this way lofes its former colour, and is in a great measure pellucid, with a mixture of fome bright fparkling colours, fuch as appear from the refraction of diamonds, and other pellucid bodies. Blood, to the naked eye, appears all red; but by a good microfcope, wherein its leffer parts appear, fhows only fome few globules of red, fwimming in a pellucid liquor; and how these red globules would appear, if glaffes could be found that yet could magnify them 1000, or 10,000 times more, is uncertain.

$12. Our Faculties of Difcovery fuited to our State. THE infinite wife Contriver of us, and all things about us, hath fitted our fenfes, faculties, and organs, to the conveniencies of life, and the bufinefs we have to do here. We are able, by our fenfes, to know and distinguifh things, and to examine them fo far, as to apply them to our ufes, and feveral ways to accommodate the exigencies of this life. We have infight enough into their admirable contrivances and wonderful effects, to admire and magnify the wisdom, power, and goodness of their Author. Such a knowledge as this, which is fuited to our prefent condition, we want not faculties

to attain.

But it appears not that God intended we fhould have a perfect, clear, and adequate knowledge of them: That perhaps is not in the comprehenfion of any finite being. We are furnished with faculties (dull and weak as they are) to difcover enough in the creatures to lead us to the knowledge of the Creator, and the knowledge of our duty; and we are fitted well enough with abilities to provide for the conveniencies of living: These are our business in this world. But were our fenfes altered and made much quicker and acuter, the appearance and outward fcheme of things would have quite another face to us, and, I am apt to think, would be inconfiftent with our being, or at leaft wellbeing, in this part of the universe which we inhabit. He that confiders how little our conftitution is able to bear a remove into parts of this air, not much higher than that we commonly breathe in, will have reafon to be fatisfied, that in this globe of earth allotted for our manfion, the allwife Architect has fuited our organs, and the bodies that are to affect them, one to another. If our sense of hearing were but 1000 times quicker than it is, how would a perpetual noise distract us? and we should, in the quieteft retirement, be less able to fleep or meditate, than in the middle of a fea-fight. Nay, if that most inftructive of our fenfes, feeing, were in any man 1000 or 100,000 times more acute than it is now by the beft microfcope, things feveral millions of times lefs than the fmalleft object of his fight now, would then be visible to his naked eyes, and fo he would come nearer the difcovery of the texture and motion of the minute parts of corporeal things, and in many of them, probably get ideas of their internal conftitutions: But then he would be in a quite different world from other people: Nothing would appear the fame to him and others; the wifible ideas of every thing would be different: So that I doubt, whether he and the rest of men could difcourfe concerning the objects of fight, or have any communication about colours, their appearances being fo wholly different. And perhaps fuch a quickness and tendernefs of fight could not en

dure bright funshine, or fo much as open day-light; nor take in but a very fmall part of any object at once, and that too only at a very near distance. And if, by the help of fuch microfcopical eyes (if I may fo call them), a man could penetrate farther than ordinary into the fecret compofition and radical texture of bodies, he would not make any great advantage by the change, if fuch an acute fight would not ferve to conduct him to the market and exchange; if he could not fee things he was to avoid, at a convenient diftance, nor distinguish things he had to do with, by thofe fenfible qualities others do. He that was fharp-fighted enough to fee the configuration of the minute particles of the fpring of a clock, and obferve upon what peculiar ftructure and impulse its elastic motion depends, would no doubt discover fomething very admirable: But if eyes fo framed could not view, at once, the hand and the characters of the hour-plate, and thereby, at a distance, fee what o'clock it was, their owner could not be much benefited by that acutenefs, which, whilft it difcovered the fecret contrivance of the parts of the machine, made him lofe its use.

13. Conjecture about Spirits.

AND here give me leave to propose an extravagant conjecture of mine, viz. that fince we have fome reason (if there be any credit to be given to the report of things that our philofophy cannot account for) to imagine, that fpirits can affume to themselves bodies of different bulk, figure, and conformation of parts; whether one great advantage fome of them have over us, may not lie in this, that they can fo frame and fhape to themselves organs of fenfation or perception, as to fuit them to their prefent defign, and the circumstances of the object they would confider. For how much would that man exceed all others in knowledge, who had but the faculty fo to alter the structure of his eyes, that one fenfe, as to make it capable of all the feveral degrees of vifion which the afliftance of glaffes (cafually at first lit on) has taught us to conceive? What wonders would he difcover, who could fo fit his eyes to all