words together in propositions so as exactly to express the agreement or disagreement of the ideas they signify. Certainty of knowledge is the perception of the agreement or disagreement of ideas as expressed in any proposition.-To be certain of the truth of any general proposition we must know the essence of each species its terms stand for. This we may easily do in all simple ideas and modes, because the real and nominal essence is the same, that is, the abstract idea, which the general term denotes, is the sole esBut in substances a real essence distinct from the nominal being supposed to determine the species, the extent of the general term is uncertain. If men would apply general terms strictly to the nominal essence alone, there would be no doubt about the truth of propositions.

sence.

I have chosen to use the scholastic terms essences and species on purpose to shew the absurdity of thinking them any other realities than abstract ideas with names affixed to them. I might perhaps have treated of these things in a better and clearer way, but that I thought it necessary to discover and remove those wrong notions of essences or species which the prevalence of scholastic learning has too generally inculcated.

The names of substances when used as they should be, for the ideas men have in their minds, carry a clear and determinate signification with them; but

will not serve for universal propositions of whose truth we can be certain; because their complex ideas are such combinations of simple ones as have no discoverable connexion or repugnancy but with very few other ideas. No one, I think, can certainly know from the colour of any body what smell, taste, sound, or tangible qualities it has, or what alterations it is capable of making on or receiving from other bodies.

How much the being and operation of particular substances in this our globe depend on causes utterly beyond our view, it is impossible for us to determine. The parts of this stupendous universe may have such a connexion, that the things of this Earth would cease to be what they are, if some incomprehensibly remote star should cease to move or be as it is.

Inquisitive and observing men may by strength of judgment, and on probabilities taken from wary observation, often guess right at what experience has not discovered; but this still is only opinion and not knowledge. Let our abstract idea of man be a body of such a shape, with sense, voluntary motion, and reason; and we cannot with certainty affirm that all men sleep by intervals;-no man can be nourished by wood or stones;-all men will be poisoned by hemlock-because these ideas have no necessary connexion or repugnancy with the nominal essence or abstract idea.

CHAP. VII..

OF MAXIMS.

MAXIMS and Axioms have passed for principles of science; and being self-evident have been supposed innate. Several other truths, not allowed to be axioms, are equally self-evident.

1st, The immediate perception of Identity or Diversity, being founded in the mind's having distinct ideas, affords as many self-evident propositions as we have distinct ideas: for we need only understand the terms to perceive the truth of what is affirmed or denied concerning the agreement or disagreement of the ideas that a man is not a horse, that blue is not red, is as self-evident as that whatever is, is.

2dly, of Co-existence, or such necessary connexion between two ideas that the existence of one always supposes that of the other, we have but few intuitive ideas. The idea of filling a place equal to the contents of its superficies being annexed to our idea of body, I think this proposition intuitive; "that two bodies cannot be in the same place."

3dly, As to the relations of modes, Mathematicians have framed many axioms concerning that of equality: as Equals taken from equals, the re

mainders will be equal. Though these are unquestionable Truths, many propositions may be found in numbers, equally if not more clear; as that one and one are equal to two.

4thly, As to real existence, that idea having no connexion with any others than those of self and a first being, we have not even demonstrative, much less intuitive knowledge,

The Rules established in the schools, that all reasonings are ex præcognitis et præconcessis, seem to make these maxims the foundation of all knowledge. I suppose they mean that these truths are the first known to the mind, and are the basis of all the other parts of knowledge.

We have shewn in Chap. 2. Book 1. that these are not the truths first known to the mind. A child certainly knows that a stranger, is not its mother, long before it knows that 'tis impossible for the same thing to be, and not to be. It is evident that our first ideas are those of particular things; and that abstract ideas are only rendered obvious by constant and familiar use, being fictions of the mind. Does it not require some pains to form the general idea of a triangle? for it must be neither oblique nor rectangle, neither equilateral, equicrural, nor scalenon, but all and none of these at once. In short, it is something imperfect, that cannot exist,—an idea comprising some parts of several different and inconsistent ideas :-yet

the mind, in this imperfect state, has need of these ideas for the communication and enlargement of knowledge.

From what has been said it follows that these Maxims are not the foundation of all our knowledge. Cannot we know that one and two are equal to three, without knowing that the whole is equal to all its parts taken together? indeed if there be any odds, the ideas whole and parts are more obscure than those of one, two, three. Scholastic men talk much of the maxims on which the sciences are built: but it has been my ill luck never to meet with any such sciences. Axioms may serve to silence wranglers, and put an end to dispute. When we find out an idea, by whose intervention we discover the connexion of two others, this is a revelation from God to us, by the voice of reason. When God declares any truth to us, this is a revelatian by the voice of his spirit. But in neither of these do we receive our knowledge from maxims; which are of no use in the discovery of unknown truths.

Mr. Newton, in his never enough to be admired book, has demonstrated several propositions, which are so many new truths and advances in Mathematical knowledge; but was not assisted by any such general maxims.

When schools were erected, and Professors taught what others had discovered, Axioms were laid down