nor, did we know them, could we discover any neceffary connection between them and any of the fecondary qualities, which is neceffary to be done before we can certainly know their neceffary co-existence. So that let our complex idea of any fpecies of fubftances be what it will, we can hardly, from the fimple ideas contained in it, certainly determine the necessary coexistence of any other quality whatfoever. Our knowledge in all these inquiries reaches very little farther than our experience. Indeed, fome few of the primary qualities have a neceffary dependence and visible connection one with another, as figure neceffarily fuppofes extenfion; receiving or communicating motion by impulfe fuppofes folidity. But though these, and perhaps fome other of our ideas have, yet there are fo few of them that have a visible connection one with another, that we can by intuition or demonftration discover the co-existence of very few of the qualities are to be found united in fubftances, and we are left only to the affiftance of our fenfes, to make known to us what qualities they contain. For of all the qualities that are co-exiftent in any fubject, without this dependence and evident connection of their ideas one with another, we cannot know certainly any two to co-exit any farther than experience, by our fenfes, informs us. Thus, though we fee the yellow colour, and upon trial find the weight, malleablenefs, fufibility, and fixedness, that are united in a piece of gold; yet be cause no one of these ideas has any evident dependence, or neceffary connection with the other, we cannot certainly know, that where any four of thefe are, the fifth will be there also, how highly probable foever it may be; because the highest probability amounts not to certainty, without which there can be no true knowledge. For this co-existence can be no farther known than it is perceived; and it cannot be perceived, but either in particular fubjects, by the obfervation of our fenfes, or in general, by the neceffary connection of the ideas themselves.

$15. Of Repugnancy to co-existence larger. As to incompatibility or repugnancy to co-existence, we may know, that any fubject can have of each fort of primary qualities, but one particular at once; v. g. each particular extenfion, figure, number of parts, motion, excludes all other of each kind. The like alfo is certain of all fenfible ideas peculiar to each fenfe; for whatever of each kind is prefent in any fubject, excludes all other of that fort; v. g. no one fubject can have two fmells or two colours at the same time. To this perhaps, will be faid, has not an opal, or an infufion of lignum nephriticum, two colours at the fame time? To which I anfwer, that these bodies, to eyes differently placed, may at the fame time afford different colours: but I take liberty alfo to fay, that to eyes differently placed, it is different parts of the object that reflect the particles of light; and therefore it is not the fame part of the object, and so not the very fame fubject, which at the fame time appears both yellow and azure: For it is as impoffible that the very fame particle of any body should at the fame time differently modify or reflect the rays of light, as that it should have two different figures and textures at the fame time.

§ 16. Of the Co-existence of Powers a very little way. BUT as to the powers of fubftances to change the fenfible qualities of other bodies, which make a great part of our inquiries about them, and is no inconfiderable branch of our knowledge, I doubt, as to thefe, whether our knowledge reaches much farther than our experience; or whether we can come to the discovery of most of these powers, and be certain that they are in any fubject, by the connection with any of thofe ideas which to us make its effence. Because the active and paffive powers of bodies, and their ways of operating, confifting in a texture and motion of parts, which we cannot by any means come to discover, it is but in very few cases we can be able to perceive their dependence on, or repugnance to any of those ideas which make our complex one of that fort of

things. I have here inftanced in the corpufcularian hypothefis, as that which is thought to go fartheft in an intelligible explication of the qualities of bodies; and I fear the weakness of human understanding is scarce able to substitute another, which will afford us a fuller and clearer difcovery of the neceffary connection and co-existence of the powers which are to be obferved united in feveral forts of them. This at least is certain, that whichever hypothefis be cleareft and trueft (for of that it is not my bufinefs to determine), our knowledge concerning corporeal fubftances will be very little advanced by any of them, till we are made to see what qualities and powers of bodies have a necessary connection or repugnancy one with another; which in the prefent ftate of philofophy, I think, we know but to a very small degree; and I doubt whether, with thofe faculties we have, we shall ever be able to carry our general knowledge (I say not particular experience) in this part much farther. Experience is that which in this part we must depend on ; and it were to be wished that it were more improved. We find the advantages fome mens generous pains have this way brought to the stock of na tural knowledge; and if others, especially the philofophers by fire, who pretend to it, had been fo wary in their obfervations, and fincere in their reports, as those who call themselves philofophers ought to have been, our acquaintance with the bodies here about us, and our infight into their powers and operations, had been yet much greater.

§ 17. Of Spirits yet narrower.

If we are at a lofs in refpect of the powers and operations of bodies, I think it is eafy to conclude, we are much more in the dark in reference to spirits; whereof we naturally have no ideas, but what we draw from that of our own, by reflecting on the operations of our own fouls within us, as far as they can come within our observation. But how inconfiderable a rank the fpirits that inhabit our bodies hold amongst thofe various and poffibly innumerable kinds of no

bler beings, and how far fhort they come of the endowments and perfections of cherubims and feraphims, and infinite forts of fpirits above us, is what, by a tranfient hint in another place, I have offered to my reader's confideration.

§ 18. 3. Of other Relations it is not cafy to say how far.

As to the third fort of our knowledge, viz. the agreement or difagreement of any of our ideas in any other relation this, as it is the largeft field of our knowledge, fo it is hard to determine how far it may extend; because the advances that are made in this part of knowledge, depending on our fagacity in finding intermediate ideas, that may fhow the relations and babitudes of ideas, whofe co-exiftence is not confidered, it is a hard matter to tell when we are at an end of such discoveries; and when reason has all the helps it is capable of, for the finding of proofs, or examining the agreement or difagreement of remote ideas. They that are ignorant of algebra cannot imagine the wonders in this kind are to be done by it: and what farther improvements and helps, advantageous to other parts of knowledge, the fagacious mind of man may yet find out, it is not eafy to determine. This at least I believe, that the ideas of quantity are not those alone that are capable of demonftration and knowledge; and that other, and perhaps more useful parts of contemplation, would afford us certainty, if vices, paffions, and domineering intereft, did not oppofe or menace fuch endeavours.

Morality capable of Demonftration.

The idea of a Supreme Being, infinite in power, goodness and wisdom, whofe workmanship we are, and on whom we depend; and the idea of ourselves, as understanding rational beings, being fuch as are clear in us, would, I fuppofe, if duly confidered and purfued, afford fuch foundations of our duty and rules of action, as might place morality amongst the fciences capable of demonftration; wherein I doubt not but from felf-evident propofitions, by neceffary confe

quences, as inconteftible as thofe in mathematics, the measures of right and wrong might be made out to any one that will apply himself with the fame indif ferency and attention to the one, as he does to the other of these fciences. The relation of other modes may certainly be perceived, as well as thofe of number and extension: and I cannot fee why they should not also be capable of demonstration, if due methods were thought on to examine or pursue their agreement or difagreement. Where there is no property, there is no injustice, is a propofition as certain as any demonftration in Euclid: for the idea of property being a right to any thing; and the idea to which the name injuftice is given, being the invasion or violation of that right; it is evident, that these ideas being thus eftablished, and these names annexed to them, I can as certainly know this propofition to be true, as that a triangle has three angles equal to two right ones. Again, No government allows abfolute liberty: The idea of government being the establishment of fociety upon certain rules or laws which require conformity to them; and the idea of abfolute liberty being for any one to do whatever he pleases; I am as capable of being certain of the truth of this propofition, as of any in the mathematics.

$ 19. Two things have made moral Ideas thought incapable of Demonftration. Their complexedness, and want of fenfible representations.

THAT which in this refpect has given the advantage to the ideas of quantity, and made them thought more capable of certainty and demonstration, is,

First, That they can be fet down and represented by fenfible marks, which have a greater and nearer correfpondence with them than any words or founds whatsoever. Diagrams drawn on paper are copies of the ideas in the mind, and not liable to the uncertainty that words carry in their fignification. An angle, circle or fquare, drawn in lines, lies open to the view, and cannot be mistaken it remains unchangeable, and may at leisure be confidered and examined, and the