BOOK I PART IV
like causes. Many of the impressions of colour,
sound, &c. are confest to be nothing but inter-
nal existences, and to arise from causes, which
no ways resemble them. These impressions are
in appearance nothing different from the other
impressions of colour, sound, &c. We conclude,
therefore, that they are, all of them, derived
from a like origin.
This principle being once admitted, all the
other doctrines of that philosophy seem to fol-
low by an easy consequence. For upon the re-
moval of sounds, colours, beat, cold, and other
sensible qualities, from the rank of continued
independent existences, we are reduced merely
to what are called primary qualities, as the only
real ones, of which we have any adequate no-
tion. These primary qualities are extension and
solidity, with their different mixtures and mod-