BOOK I PART IV
true with regard to extension; and have shewn
that it is impossible to conceive extension, but
as composed of parts, endowed with colour or
solidity. The idea of extension is a compound
idea; but as it is not compounded of an infi-
nite number of parts or inferior ideas, it must
at last resolve itself into such as are perfectly
simple and indivisible. These simple and indi-
visible parts, not being ideas of extension, must
be non entities, unless conceived as coloured or
solid. Colour is excluded from any real exis-
tence. The reality, therefore, of our idea of ex-
tension depends upon the reality of that of so-
lidity, nor can the former be just while the latter
is chimerical. Let us, then, lend our attention to
the examination of the idea of solidity.
The idea of solidity is that of two objects,
which being impelled by the utmost force, can-