particular thing to the idea [that] it had before settled with a Name to it. But these considerations of Truth, either having been before taken notice of, or not being much to our present purpose, it may suffice here only to have mentioned them.

CHAPTER VI.*

OF UNIVERSAL PROPOSITIONS, THEIR TRUTH AND CER

TAINTY,

General truths hardly to be understood but in verbal propositions. All the Knowledge we have being only of particular or general Truths, it is evident that whatever may be done in the former of these, the latter, which is that which with reason is most sought after, can never be well made known, and is very seldom apprehended, but as conceived and expressed in Words. It is not therefore out of our way, in the examination of our Knowledge, to inquire into the truth and certainty of universal propositions.

Certainty twofold, of truth and of knowledge.—But that we may not be misled in this case by that which is the danger everywhere, I mean by the doubtfulness of terms, it is fit to observe that certainty is twofold; certainty of Truth, and certainty of Knowledge. Certainty of Truth is when Words are so put together in Propo

* The student should read Chap. XXIII. of Book II. and Chap. III. of Book III. in immediate connexion with the present; because much essential matter is here omitted, as being but a recapitulation of arguments already advanced in those chapters.-ED.

Cer

sitions as exactly to express the agreement or disagreement of the ideas they stand for, as really it is. tainty of Knowledge is to perceive the agreement or disagreement of Ideas, as expressed in any Proposition. This we usually call knowing,' or 'being certain of' the truth of, any Proposition.

No proposition can be known to be true, where the essence of each species mentioned is not known.-Now, because we cannot be certain of the truth of any general proposition unless we know the precise bounds and extent of the species [which] its terms stand for, it is necessary we should know the Essence of each species, which is that which constitutes and bounds it. This, in all Simple Ideas and Modes, is not hard to do. For in these the Real and Nominal Essence being the same, or, which is all one, the abstract idea, which the general term stands for, being the sole essence and boundary that is or can be supposed of the species, there can be no doubt how far the species extends, or what things are comprehended under each term: which, it is evident, are all that have an exact conformity with the idea it stands for, and no other. But in Substances, wherein a Real Essence distinct from the Nominal is supposed to constitute, determine, and bound the species, the extent of the general word is very uncertain: because, not knowing this real Essence, we cannot know what is or is not of that species, and consequently what may or may not with certainty be affirmed of it. But where the Nominal Essence is kept to as the boundary of each species, and men extend the application of any general term no farther than to the particular things in which the complex idea

it stands for is to be found, they are in no danger to mistake the bounds of each species, nor can be in doubt, on this account, whether any propositions be true. I have chose[n] to explain this uncertainty of propositions in this scholastic way, and have made use of the terms 'essences' and 'species,' on purpose to show the absurdity and inconvenience there is to think of them as of any other sort of realities, than [as being] barely— Abstract ideas with Names to them.

This more particularly concerns substances.-The Names of Substances, then, whenever made to stand for species which are supposed to be constituted by Real Essences which we know not, are not capable to convey certainty to the Understanding: of the Truth of general propositions made up of such terms we cannot be sure; since it is impossible for us to know that this or that quality or idea has a necessary connexion with a Real Essence, of which we have no idea at all, whatever species that supposed Real Essence may be imagined to constitute.

The truth of few universal propositions concerning substances is to be known.—On the other side, the Names of Substances, when made use of, as they should be, for the ideas [that] men have in their minds, though they carry a clear and determined signification with them, will not yet serve us to make many universal Propositions, of whose truth we can be certain. Not because in this use of them we are uncertain what things are signified by them, but because the Complex ideas [which] they stand for are such combinations of Simple ones as carry not with them any discoverable connexion with, or repugnancy [to], but a very few other ideas.

Because co-existence of ideas in few cases is to be known. -The Complex ideas that our Names of the species of Substances properly stand for, are collections of such qualities as have been observed to co-exist in an unknown substratum which we call Substance;' but what other qualities necessarily co-exist with such combinations, we cannot certainly know, unless we can discover their natural dependence; which in their Primary Qualities we can go but a very little way in; and in all their Secondary Qualities we can discover no connexion at all, for the reasons mentioned [in] Chap

ter III.

As far as any such co-existence can be known, so far universal propositions may be certain.—So far as any Complex idea of any 'sort' of Substances contains in it any Simple idea whose necessary co-existence with any other may be discovered, so far universal propositions may with certainty be made concerning it: v. g. could any one discover a necessary connexion between malleableness and the colour or weight of 'gold,' or any other part of the Complex idea signified by that name, he might make a certain universal proposition concerning 'gold' in this respect; and the real truth of this proposition, 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.'

Judgment may reach farther, but that is not knowledge. -We are not therefore to wonder if certainty be to be found in very few general propositions made concerning Substances: our knowledge of their qualities and properties go[es] very seldom farther than our senses

reach and inform us. Possibly inquisitive and observing men may, by strength of judgment, penetrate farther; and on probabilities taken from wary observation, and hints well laid together, often guess right at what experience has not yet discovered to them. But this is but guessing still; it amounts only to opinion, and has not that certainty which is requisite to Knowledge. For all general Knowledge lies only in our own thoughts, and consists barely in the contemplation of our own Abstract ideas.

What is requisite for our knowledge of substances.-Before we can have any tolerable Knowledge of this kind, we must know, First, what changes the Primary Qualities of one body do regularly produce in the primary qualities of another, and how [they produce them]. Secondly, what Primary Qualities of any body produce certain sensations or ideas in us. This is in truth no less than to know all the effects of Matter under its divers modifications of bulk, figure, cohesion of parts, motion, and rest; which, I think, every body will allow, is utterly impossible to be known by us without Revelation.

Wherein lies the general certainty of propositions.-To conclude: general Propositions, of what kind soever, are then only capable of certainty, when the terms used in them stand for such ideas whose agreement or disagreement, as there expressed, is capable to be discovered by us. And we are then certain of their truth or falsehood, when we perceive the ideas the terms stand for to agree or not agree, according as they are affirmed or denied one of another. Whence we may take notice, that