senses, a thing I have seen, it is not in order to understand better the
same object which I had perceived by sight, the object of one sense not
being perceived by the other senses. And, when I look through a
microscope, it is not that I may perceive more clearly what I perceived
already with my bare eyes; the object perceived by the glass being quite
different from the former. But, in both cases, my aim is only to know
what ideas are connected together; and the more a man knows of the
connexion of ideas, the more he is said to know of the nature of things.
What, therefore, if our ideas are variable; what if our senses are not in
all circumstances affected with the same appearances. It will not thence
follow they are not to be trusted; or that they are inconsistent either
with themselves or anything else: except it be with your preconceived
notion of (I know not what) one single, unchanged, unperceivable, real
Nature, marked by each name. Which prejudice seems to have taken its rise
from not rightly understanding the common language of men, speaking
of several distinct ideas as united into one thing by the mind. And,
indeed, there is cause to suspect several erroneous conceits of the
philosophers are owing to the same original: while they began to build
their schemes not so much on notions as on words, which were framed by
the vulgar, merely for conveniency and dispatch in the common actions of
life, without any regard to speculation.

HYL. Methinks I apprehend your meaning.

PHIL. It is your opinion the ideas we perceive by our senses are not
real things, but images or copies of them. Our knowledge, therefore, is
no farther real than as our ideas are the true REPRESENTATIONS OF THOSE
ORIGINALS. But, as these supposed originals are in themselves unknown,
it is impossible to know how far our ideas resemble them; or whether they
resemble them at all. We cannot, therefore, be sure we have any real
knowledge. Farther, as our ideas are perpetually varied, without any
change in the supposed real things, it necessarily follows they cannot
all be true copies of them: or, if some are and others are not, it is
impossible to distinguish the former from the latter. And this plunges us
yet deeper in uncertainty. Again, when we consider the point, we cannot
conceive how any idea, or anything like an idea, should have an absolute
existence out of a mind: nor consequently, according to you, how there
should be any real thing in nat