previously cited admissions; if he only means, on the other hand, that
his pure spirit could not get very far on in his geometry, it may be
true or not; but it is in contradiction with his previous assertion,
that such a pure spirit could never attain to know as much as the
first elements of plane geometry.

Another source of confusion, which arises out of Berkeley's
insufficient exactness in the use of language, is to be found in what
he says about solidity, in discussing Molyneux's problem, whether a
man born blind and having learned to distinguish between a cube and a
sphere, could, on receiving his sight, tell the one from the other
by vision. Berkeley agrees with Locke that he could not, and adds the
following reflection:--

"Cube, sphere, table, are words he has known applied to things
perceivable by touch, but to things perfectly intangible
he never knew them applied. Those words in their wonted
application always marked out to his mind bodies or solid
things which were perceived by the resistance they gave. But
there is no solidity, no resistance or protrusion perceived by
sight."

Here "solidity" means resistance to pressure, which is apprehended by
the muscular sense; but when in section 154 Berkeley says of his pure
intelligence--

"It is certain that the aforesaid intelligence could have no
idea of a solid or quantity of three dimensions, which follows
from its not having any idea of distance "--