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      §16. A Child knows not that Three and Four are equal to Seven,
till he comes to be able to count to Seven, and has got the Name and
Idea of Equality: and then upon the explaining those Words, he
presently assents to, or rather perceives the Truth of that Propo-
sition. But neither does he then readily assent, because it is an
innate Truth, nor was his Assent wanting, till then, because he
wanted the Use of Reason; but the Truth of it appears to him, as soon
as he has setled in his Mind the clear and distinct Ideas, that these
Names stand for: And then, he knows the Truth of that Proposition,
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upon the same Grounds, and by the same means, that he knew
before, That a Rod and Cherry are not the same thing; and upon the
same Grounds also, that he may come to know afterwards, That it is
impossible for the same thing to be, and not to be, as shall be more fully
shewn hereafter. So that the later it is before any one comes to have
those general Ideas, about which those Maxims are; or to know the
Signification of those general Terms, that stand for them; or to put
together in his Mind, the Ideas they stand for: the later also will it
be, before he comes to assent to those Maxims, whose Terms, with
the Ideas they stand for, being no more innate, than those of a Cat
or a Weesel, he must stay till Time and Observation have ac-
quainted him with them; and then he will be in a Capacity to know
the Truth of these Maxims, upon the first Occasion, that shall
make him put together those Ideas in his Mind, and observe,
whether they agree or disagree, according as is expressed in those
Propositions. And therefore it is, That a Man knows that Eighteen
and Nineteen, are equal to Thirty Seven, by the same self-Evidence,
that he knows One and Two to be equal to Three: Yet, a Child
knows this, not so soon as the other; not for want of the use of
Reason: but because the Ideas the Words Eighteen, Nineteen, and
Thirty seven stand for, are not so soon got, as those, which are
signify’d by One, Two, and Three.
Locke Hum I, 2, §16, pp. 55-56