OF HUMAN UNDERSTANDING.

BOOK IV.-CHAP. I.

OF KNOWLEDGE IN GENERAL.

1. Our Knowledge converfant about our Ideas.
INCE the mind, in all its thoughts and reafon-

ideas, which it alone does or can contemplate, it is
evident, that our knowledge is only converfant about
them.

§ 2. Knowledge is the Perception of the Agreement
or Difagreement of two Ideas.

KNOWLEDGE then feems to me to be nothing but the
perception of the connection and agreement, or difagree-
ment and repugnancy of any of our Ideas. In this
alone it confifts. Where this perception is, there is
knowledge; and where it is not, there, though we
may fancy, guess, or believe, yet we always come fhort
of knowledge. For when we know that white is not
black, what do we elfe but perceive that these two
ideas do not agree? when we poffefs ourselves with
the utmost security of the demonftration, that the three
angles of a triangle are equal to two right ones, what
do we more but perceive, that equality to two right
ones, does neceffarily agree to, and is infeparable from
the three angles of a triangle?

$3. This Agreement fourfold.

BUT to understand a little more diftinctly, wherein this
agreement or difagreement confifts, I think we may
reduce it all to thefe four forts;

1. Identity, or diverfity.

2. Relation.

3. Co-existence, or neceffary connection,
4. Real exiflence.

$4.1. Of Identity or Diverfity.

FIRST, AS to the firft fort of agreement or disagree-
ment, viz. identity or diverfity, It is the first act of
the mind, when it has any fentiments or ideas at all, to
perceive its ideas; and fo far as it perceives them, to
know each what it is, and thereby alfo to perceive
their difference, and that one is not another. This is
fo abfolutely neceffary, that without it there could be
no knowledge, no reasoning, no imagination, no dif-
tinct thoughts at all. By this the mind clearly and
infallibly perceives each idea to agree with itfelf, and
to be what it is; and all diftin&t ideas to difagree,
i. e. the one not to be the other: and this it does
without pains, labour or deduction, but at first view,
by its natural power of perception and diftinction.
And though men of art have reduced this into thofe
general rules, What is, is; and it is impoffible for the
fame thing to be, and not to be; for ready application
in all cafes, wherein there may be occafion to reflect
on it; yet it is certain, that the first exercise of this
faculty is about particular ideas. A man infallibly
knows, as foon as ever he has them in his mind, that
the ideas he calls white and round, are the very ideas
they are, and that they are not other ideas which he
calls red or fquare: Nor can any maxim or propofi-
tion in the world make him know it clearer or furer
than he did before, and without any fuch general rule.
This then is the first agreement or difagreement, which
the mind perceives in its ideas; which it always per-
ceives at first fight: and if there ever happen any
doubt about it, it will always be found to be about the
names, and not the ideas themfelves, whofe identity
and diverfity will always be perceived, as foon and as
clearly as the ideas themfelves are, nor can it poffibly
be otherwife.

111

$5. 2. Relative.

SECONDLY, The next fort, of agreement, or difagreement, the mind perceives in any of its ideas, may, I think, be called relative, and is nothing but the perception of the relation between any two ideas, of what kind foever, whether fubftances, modes, or any other. For fince all diftin&t ideas must eternally be known not to be the fame, and fo be univerfally and conftantly denied one of another, there could be no room for any pofitive knowledge at all, if we could not perceive any relation between our ideas, and find out the agreement or difagreement they have one with another, in feveral ways the mind takes of comparing

them.

$6. 3. Of Co-existence.

THIRDLY, The third fort of agreement, or disagreement, to be found in our ideas, which the perception of the mind is employed about, is co-existence, or nonco-exilence in the fame fubject; and this belongs particularly to fubftances. Thus, when we pronounce concerning gold that it is fixed, our knowledge of this truth amounts to no more but this, that fixednefs, or a power to remain in the fire unconfumed, is an idea that always accompanies and is joined with that particular fort of yellownefs, weight, fufibility, malleablenefs, and folubility in aqua regia, which make our complex idea, fignified by the word gold.

$7. 4. Of real Existence.

FOURTHLY, The fourth and last fort is that of actual real exiftence agreeing to any idea. Within thefe four forts of agreement or difagreement, is, I fuppofe, contained all the knowledge we have, or are capable of: For all the inquiries that we can make concerning any of our ideas, all that we know or can affirm concerning any of them, is, that it is, or is not, the fame with fome other; that it does, or does not, always co-exift with fome other idea in the fame fubject; that it has this or that relation to fome other idea; or that it has a real exiftence without the mind. Thus blue is not yellow, is of identity: Two triangles upon equal bafes between

two parallels are equal, is of relation: Iron is fufceptible of magnetical impreffions is of co-existence: God is, is of real exiftence. Though identity and co-exiftence are truly nothing but relations, yet they are fo peculiar ways of agreement or difagreement of our ideas, that they deferve well to be confidered as distinct heads, and not under relation in general; fince they are so different grounds of affirmation and negation, as will eafily appear to any one, who will but reflect on what is faid in feveral places of this effay. I should now proceed to examine the feveral degrees of our knowledge, but that it is neceffary firft to confider the different acceptations of the word knowledge.

8. Knowledge actual or habitual.

THERE are feveral ways wherein the mind is poffeffed of truth, each of which is called knowledge.

1. There is actual knowledge, which is the present view the mind has of the agreement or difagreement of any of its ideas, or of the relation they have one to another.

2. A man is faid to know any propofition, which having been once laid before his thoughts, he evidently perceived the agreement or difagreement of the ideas whereof it confifts; and fo lodged it in his memory, that whenever that propofition comes again to be reflected on, he, without doubt or hefitation, embraces the right fide, affents to, and is certain of the truth of it. This, I think, one may call babitual knowledge and thus a man may be faid to know all those truths which are lodged in his memory, by a foregoing clear and full perception, whereof the mind is affured paft doubt, as often as it has occafion to reflect on them. For our finite understandings being able to think clearly and diflinctly but on one thing at once, if men had no knowledge of any more than what they actually thought on, they would all be very ignorant; and he that knew moft would know but one truth, that being all he was able to think on at one time.

§ 9. Habitual Knowledge twofold. Or habitual knowledge, there are alfo, vulgarly speaking, two degrees:

First, The one is of fuch truths laid up in the memory, as whenever they occur to the mind, it actually perceives the relation is between thofe ideas. And this is in all thofe truths, whereof we have an intuitive. knowledge; where the ideas themselves, by an immediate view, difcover their agreement or disagreement one with another.

Secondly, The other is of fuch truths, whereof the mind having been convinced, it retains the memory of the conviction without the proofs. Thus a man that remembers certainly that he once perceived the demonstration, that the three angles of a triangle are equal to two right ones, is certain that he knows it, because he cannot doubt of the truth of it. In his adherence to a truth, where the demonftration by which it was at first known is forgot, though a man may be thought rather to believe his memory than really to know; and this way of entertaining a truth feemed formerly to me like fomething between opinion and knowledge; a fort of affurance which exceeds bare belief, for that relies on the teftimony of another : yet upon a due examination I find it comes not short of perfect certainty, and is in effect true knowledge. That which is apt to mislead our first thoughts into a mistake in this matter, is, that the agreement or difagreement of the ideas in this cafe is not perceived, as it was at first, by an actual view of all the intermediate ideas, whereby the agreement or difagreement of thofe in the propofition was at firft perceived; but by other intermediate ideas, that show the agree ment or difagreement of the ideas contained in the propofition whose certainty we remember. For example, in this propofition, that the three angles of a triangle are equal to two right ones, one who has feen and clearly perceived the demonftration of this truth, knows it to be true, when that demonftration is gone out of his mind; fo that at present it is not