ns, nor even the sensations which compose the
objects of perception, can exist otherwise than in a mind perceiving
them. It is impossible that objects should have any existence out of the
minds for which they exist; to conceive them as existing unperceived is
a mere abstraction. Whence it follows that there is no other substance
but spirit, or that which perceives.

Some, indeed, distinguish between "primary" and "secondary" qualities,
and hold that the former, such as extension, figure, motion, and
solidity, have some existence outside of the mind in an unthinking
substance which they call "matter." But extension, figure, and motion
are only ideas existing in the mind, and neither these ideas nor their
archetypes can exist in an unperceiving substance. The very notion of
what is called "matter" involves a contradiction within it. Not only
primary and secondary qualities alike, but also "great" and "small,"
"swift" and "slow," "extension," "number," and even "unity" itself,
being all of them purely relative, exist only in the mind. The
conception of "material substance" has no meaning but that of "being" in
general.

Even if we were to give to the materialists their "external bodies,"
they are by their own confession no nearer to knowledge how our ideas
are produced, since they own themselves unable to comprehend in what
manner body can act upon spirit, or how it is possible that it should
imprint any idea on the mind.

It is evident that the production of ideas in our minds can be no reason
why we should suppose corporeal substances to exist, since the rise of
those ideas is acknowledged to remain equally inexplicable with or
without the supposition of material existences. In short, if there were
external bodies, it is impossible that we should ever come to know it;
and if there were not, we should have the same reasons to think there
were, that we have now. We perceive a continual succession of ideas;
some are anew excited, others are changed or totally disappear. There
is, therefore, some cause of these ideas, whereon they depend, which
produces and changes them. This cause must be a substance; but it has
been shown that there is no corporeal or material substance. It remains,
therefore, that the cause of ideas is an incorporeal active substance or
spirit.

A spirit is one simple, undivided, active being; as it perceives ideas
it is called the "understanding," and as it produces or otherwise
operates about them,