4. As to identity and diversity, all propositions are equally self-evident.
I. For, First, The immediate perception of
the agreement or disagreement of identity being founded in the mind's having distinct ideas, this affords us as
many self-evident propositions as we have distinct ideas. Every one that has any knowledge at all, has, as the
foundation of it, various and distinct ideas: and it is the first act of the mind (without which it can never be
capable of any knowledge) to know every one of its ideas by itself, and distinguish it from others. Every one finds
in himself, that he knows the ideas he has; that he knows also, when any one is in his understanding, and what it
is; and that when more than one are there, he knows them distinctly and unconfusedly one from another; which
always being so, (it being impossible but that he should perceive what he perceives,) he can never be in doubt
when any idea is in his mind, that it is there, and is that idea it is; and that two distinct ideas, when they are in his
mind, are there, and are not one and the same idea. So that all such affirmations and negations are made without
any possibility of doubt, uncertainty, or hesitation, and must necessarily be assented to as soon as understood; that
is, as soon as we have in our minds determined ideas, which the terms in the proposition stand for. And, therefore,
whenever the mind with attention considers any proposition, so as to perceive the two ideas signified by the terms,
and affirmed or denied one of the other to be the same or different; it is presently and infallibly certain of the truth
of such a proposition; and this equally whether these propositions be in terms standing for more general ideas, or
such as are less so: v.g. whether the general idea of Being be affirmed of itself, as in this proposition, "whatsoever
is, is"; or a more particular idea be affirmed of itself, as "a man is a man"; or, "whatsoever is white is white"; or
whether the idea of being in general be denied of not-Being, which is the only (if I may so call it) idea different
from it, as in this other proposition, "it is impossible for the same thing to be and not to be": or any idea of any
particular being be denied of another different from it, as "a man is not a horse"; "red is not blue." The difference
of the ideas, as soon as the terms are understood, makes the truth of the proposition presently visible, and that
with an equal certainty and easiness in the less as well as the more general propositions; and all for the same
reason, viz., because the mind perceives, in any ideas that it has, the same idea to be the same with itself; and two
different ideas to be different, and not the same; and this it is equally certain of, whether these ideas be more or
less general, abstract, and comprehensive. It is not, therefore, alone to these two general
propositions--"whatsoever is, is"; and "it is impossible for the same thing to be and not to be"--that this sort of
self-evidence belongs by any peculiar right. The perception of being, or not being, belongs no more to these vague
ideas, signified by the terms whatsoever, and thing, than it does to any other ideas. These two general maxims,
amounting to no more, in short, but this, that the same is the same, and the same is not different, are truths known
in more particular instances, as well as in those general maxims; and known also in particular instances, before
these general maxims are ever thought on; and draw all their force from the discernment of the mind employed
about particular ideas. There is nothing more visible than that the mind, without the help of any proof, or
reflection on either of these general propositions, perceives so clearly, and knows so certainly, that the idea of
white is the idea of white, and not the idea of blue; and that the idea of white, when it is in the mind, is there, and
is not absent; that the consideration of these axioms can add nothing to the evidence or certainty of its knowledge.
Just so it is (as every one may experiment in himself) in all the ideas a man has in his mind: he knows each to be
itself, and not to be another; and to be in his mind, and not away when it is there, with a certainty that cannot be
greater; and, therefore, the truth of no general proposition can be known with a greater certainty, nor add anything
to this. So that, in respect of identity, our intuitive knowledge reaches as far as our ideas. And we are capable of
making as many self-evident propositions, as we have names for distinct ideas. And I appeal to every one's own
mind, whether this proposition, "a circle is a circle," be not as self-evident a proposition as that consisting of more
general terms, "whatsoever is, is"; and again, whether this proposition, "blue is not red," be not a proposition that
the mind can no more doubt of, as soon as it understands the words, than it does of that axiom, "it is impossible
for the same thing to be and not to be?" And so of all the like.
