viz. 1. Because we know not the real conftitutions of substances, on which each fecondary quality particularly depends. 2. Did we know that, it would ferve us only for experimental (not univerfal) knowledge, and reach with certainty no farther than that bare inftance; because our understandings can difcover no conceivable connection between any fecondary quality, and any modification whatfoever of any of the primary ones. And therefore there are very few general propofitions to be made concerning fubftances, which can carry with them undoubted certainty. 8. Inftance in Gold. ALL gold is fixed, is a propofition whofe truth we cannot be certain of, how univerfally foever it be believed. For if, according to the ufelefs imagination of the schools, any one fuppofes the term gold to ftand for .a fpecies of things fet out by nature, by a real effence belonging to it, it is evident he knows not what particular fubftances are of that species; and fo cannot, with certainty, affirm any thing univerfally of gold. But if he makes gold stand for a fpecies determined by its nominal effence, let the nominal ef fence, for example, be the complex idea of a body of a certain yellow colour, malleable, fufible, and beavier than any other known; in this proper ufe of the word gold, there is no difficulty to know what is or is not gold. But yet no other quality can with certainty be univerfally affirmed or denied of gold, but what hath a difcoverable connection or inconfiftency with that nominal eflence. Fixednefs, for example, having no neceffary connection, that we can difcover, with the colour, weight, or any other fimple idea of our complex one, or with the whole combination together, it is impoffible that we should certainly know the truth of this propofition, that all gold is fixed. $9. As there is no difcoverable connection between fixedefs, and the colour, weight, and other fimple ideas of that nominal effence of gold; fo if we make our complex idea of gold, a body yellow, fufible, ductile, Book IV. weighty, and fixed, we fhall be at the fame uncertainty concerning folubility in aqua regia, and for the fame reafon; fince we can never, from confideration of the ideas themfelves, with certainty affirm or deny of a body, whofe complex idea is made up of yellow, very weighty, ductile, fufible, and fixed, that it is foluble in aqua regia, and fo on of the rest of its qualities. I would gladly meet with one general affirmation concerning any quality of gold, that any one can certainly know is true. It will, no doubt, be prefently objected, is not this an univerfal certain propofition, all gold is malleable? To which I answer, it is a very certain propofition, if malleableness be a part of the complex idea the word gold ftands for. But then here is nothing affirmed of gold, but that that found stands for an idea in which malleableness is contained and fuch a fort of truth and certainty as this, it is to fay a centaur is four-footed. But if malleablenefs makes not a part of the specific effence the name gold stands for, it is plain, all gold is malleable, is not a certain propofition; becaufe, let the complex idea of gold be made up of which foever of its other qualities you please, malleablenefs will not appear to depend on that complex idea, nor follow from any fimple one contained in it; the connection that malleablene/shas (if it has any) with those other qualities, being only by the intervention of the real conftitution of its infenfible parts; which, fince we know not, it is impoffible we should perceive that connection, unless we could difcover that which ties them together. : $10. As far as any fuch co-existence can be known, fo far univerfal Propofitions may be certain. But this will go but a little way, becaufe, THE more, indeed, of thefe co-exifting qualities we unite into one complex idea, under one name, the more precife and determinate we make the fignification of that word; but yet never make it thereby more capable of universal certainty, in respect of other qualities not contained in our complex idea, fince we perceive not their connection or dependence one on another, being ignorant both of that real conftitution in which they are all founded, and alfo how they flow from it; for the chief part of our knowledge concerning fubftances, is not, as in other things, barely of the relation of two ideas that may exit feparately, but is of the neceffary connection and co-existence of feveral diftinct ideas in the fame fubject, or of their repugnancy fo to co-exist. Could we begin at the other end, and discover what it was wherein that colour confifted, what made a body lighter or heavier, what texture of parts made it malleable, fufible, and fixed, and fit to be diffolved in this fort of liquor, and not in another; if (1 say) we had fuch an idea as this of bodies, and could perceive wherein all fenfible qualities originally confit, and how they are produced, we might frame such abstract ideas of them, as would furnish us with matter of more general knowledge, and enable us to make univerfal propofitions, that fhould carry general truth and certainty with them; but whilft our complex ideas of the forts of fubftances are fo remote from that internal real conftitution on which their fenfible qualities depend, and are made up of nothing but an imperfect collection of thofe apparent qualities our fenfes can difcover, there can be very few general propofitions concerning fubftances, of whose real truth we can be certainly affured, fince there are but few fimple ideas, of whofe connection and neceffary co-existence we can have certain and undoubted knowledge. I imagine, amongst all the fe condary qualities of fubftances, and the powers relating to them, there cannot any two be named, whofe neceffary co-existence, or repugnance to co-exift, can certainly be known, unless in thofe of the fame fenfe, which neceffarily exclude one another, as I have else. where fhowed. No one, I think, by the colour that is in any body, can certainly know what smell, taste, found, or tangible qualities it has, nor what alterations it is capable to make or receive on or from other bodies. The fame may be faid of the found or taste, &c. Our specific names of fubftances ftanding for any collections of fuch ideas, it is not to be wondered, that we can with them make very few general propofitions of undoubted real certainty; but yet so far as any complex idea of any fort of fubftances contains in it any fimple idea, whofe neceffary co-existence with any other may be discovered, fo far universal propofitions may with certainty be made concerning it; v. g. could any one difcover a neceffary connection be tween malleableness and the colour or weight of gold, or any other part of the complex idea fignified by that name, he might make a certain univerfal propofition concerning gold in this refpect; and the real truth of this propofition, that all gold is malleable, would be as certain as of this, the three angles of all right lined triangles are equal to two right ones. § 11. The Qualities which make our complex Ideas of Subftances depend mostly on external, remote, and unperceived Caufes. HAD we fuch ideas of substances, as to know what real conftitutions produce thofe fenfible qualities we find in them, and how thofe qualities flowed from thence, we could by the fpecific ideas of their real effences in our own minds, more certainly find out their properties, and discover what qualities they had or had not, than we can now by our fenfes; and to know the properties of gold, it would be no more neceffary that gold should exift, and that we should make experiments upon it, than it is neceffary for the knowing the properties of a triangle, that a triangle fhould exist in any matter; the iden in our minds would ferve for the one as well as the other; but we are so far from being admitted into the secrets of Nature, that we scarce fo much as ever approach the first entrance towards them; for we are wont to confider the fubftances we meet with each of them as an entire thing by itself, having all its qualities in itself, and independent of other things; overlooking, for the most part, the operations of thofe invifible fluids they are encompaffed with, aud upon whofe motions and ope rations depend the greateft part of thofe qualities which are taken notice of in them, and are made by us the inherent marks of distinction whereby we know and denominate them. Put a piece of gold any where by itself, feparate from the reach and influence of all other bodies, it will immediately lofe all its colour and weight, and perhaps malleablenefs too; which, for ought I know, would be changed into perfect friability. Water, in which to us fluidity is an effential quality, left to itself, would ceafe to be fluid; but if inanimate bodies owe fo much of their present state to other bodies without them, that they would not be what they appear to us, were those bodies that environ them removed, it is yet more fo in vegetables, which are nourished, grow, and produce leaves, flowers and feeds, in a conftant fucceffion; and if we look a little nearer into the state of animals, we shall find that their dependence, as to life, motion, and the moft confiderable qualities to be observed in them, is fo wholly on extrinfical caufes and qualities of other bodies that make no part of them, that they cannot fubfift a moment without them; though yet those bodies on which they depend are little taken notice. of, and make no part of the complex ideas we frame of those animals. Take the air but a minute from the greatest part of living creatures, and they prefently lofe fenfe, life, and motion. This the neceffity of breathing has forced into our knowledge; but how many other extrinfical, and poffibly very remote bodies, do the fprings of thofe admirable machines dcpend on, which are not vulgarly obferved, or fo much as thought on; and how many are there, which the fevereft inquiry can never difcover? The inhabitants of this spot of the univerfe, though removed fo many millions of miles from the fun, yet depend so much on the duly tempered motion of particles coming from or agitated by it, that were this earth removed but a small part of that diftance out of its prefent fituation, and placed a little farther or nearer that fource of heat, it is more than probable that the greatest part of the animals in it would immediately perish; since |