ng us, that a
mis-shaped foetus is a MONSTER, run into the same fault they are arguing
against; by constituting a species between man and beast. For what else,
I pray, is their monster in the case, (if the word monster signifies
anything at all,) but something neither man nor beast, but partaking
somewhat of either? And just so is the CHANGELING before mentioned. So
necessary is it to quit the common notion of species and essences, if we
will truly look into the nature of things, and examine them by what our
faculties can discover in them as they exist, and not by groundless
fancies that have been taken up about them.

17. Words and Species.

I have mentioned this here, because I think we cannot be too cautious
that words and species, in the ordinary notions which we have been used
to of them, impose not on us. For I am apt to think therein lies one
great obstacle to our clear and distinct knowledge, especially in
reference to substances: and from thence has rose a great part of the
difficulties about truth and certainty. Would we accustom ourselves to
separate our contemplations and reasonings from words, we might in a
great measure remedy this inconvenience within our own thoughts: but yet
it would still disturb us in our discourse with others, as long as we
retained the opinion, that SPECIES and their ESSENCES were anything else
but our abstract ideas (such as they are) with names annexed to them, to
be the signs of them.

18. Recapitulation.

Wherever we perceive the agreement or disagreement of any of our ideas,
there is certain knowledge: and wherever we are sure those ideas agree
with the reality of things, there is certain real knowledge. Of which
agreement of our ideas with the reality of things, having here given
the marks, I think, I have shown WHEREIN IT IS THAT CERTAINTY, REAL
CERTAINTY, CONSISTS. Which, whatever it was to others, was, I confess,
to me heretofore, one of those desiderata which I found great want of.

CHAPTER V. OF TRUTH IN GENERAL.

1. What Truth is.

WHAT is truth? was an inquiry many ages since; and it being that which
all mankind either do, or pretend to search after, it cannot but be
worth our while carefully to examine wherein it consists; and so
acquaint ourselves with the nature of it, as to observe how the mind
distinguishes it from falsehood.

2. A right joining or separating of signs, i.e. either Ideas or Words.

Truth, then, seems to me, in the proper imp