Certainty
of truth is, when words are so put together in propositions as exactly
to express the agreement or disagreement of the ideas they stand
for, as really it is. Certainty of knowledge is to perceive the
agreement or disagreement of ideas, as expressed in any proposition.
This we usually call knowing, or being certain of the truth of any
proposition.
4. No proposition can be certainly known to be true, where the
real essence of each species mentioned is not known. Now, because we
cannot be certain of the truth of any general proposition, unless we
know the precise bounds and extent of the species its terms stand for,
it is necessary we should know the essence of each species, which is
that which constitutes and bounds it.
This, in all simple ideas and modes, is not hard to do. For in these
the real and nominal essence being the same, or, which is all one, the
abstract idea which the general term stands for being the sole essence
and boundary that is or can be supposed of the species, there can be
no doubt how far the species extends, or what things are
comprehended under each term; which, it is evident, are all that
have an exact conformity with the idea it stands for, and no other.
But in substances, wherein a real essence, distinct from the
nominal, is supposed to constitute, determine, and bound the
species, the extent of the general word is very uncertain; because,
not knowing this real essence, we cannot know what is, or what is
not of that species; and, consequently, what may or may not with
certainty be affirmed of it.
Pages:
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871