5. This more particularly concerns substances.
The names of substances, then, whenever made to stand for species
which are supposed to be constituted by real essences which we know not, are not capable to convey certainty to
the understanding. Of the truth of general propositions made up of such terms we cannot be sure. The reason
whereof is plain: for how can we be sure that this or that quality is in gold, when we know not what is or is not
gold? Since in this way of speaking, nothing is gold but what partakes of an essence, which we, not knowing,
cannot know where it is or is not, and so cannot be sure that any parcel of matter in the world is or is not in this
sense gold; being incurably ignorant whether it has or has not that which makes anything to be called gold; i.e.,
that real essence of gold whereof we have no idea at all. This being as impossible for us to know as it is for a blind
man to tell in what flower the colour of a pansy is or is not to be found, whilst he has no idea of the colour of a
pansy at an. Or if we could (which is impossible) certainly know where a real essence, which we know not, is,
v.g. in what parcels of matter the real essence of gold is, yet could we not be sure that this or that quality could
with truth be affirmed of gold; since it is impossible for us to know that this or that quality or idea has a necessary
connexion with a real essence of which we have no idea at all, whatever species that supposed real essence may
be imagined to constitute.
