y be a real something which
is the cause of all our impressions; that sensations, though not
likenesses, are symbols of that something; and that the part of that
something, which we call the nervous system, is an apparatus for
supplying us with a sort of algebra of fact, based on those symbols. A
brain may be the machinery by which the material universe becomes
conscious of itself. But it is important to notice that, even if this
conception of the universe and of the relation of consciousness to its
other components should be true, we should, nevertheless, be still bound
by the limits of thought, still unable to refute the arguments of pure
idealism. The more completely the materialistic position is admitted,
the easier is it to show that the idealistic position is unassailable,
if the idealist confines himself within the limits of positive
knowledge.

Hume deals with the questions whether all our ideas are derived from
experience, or whether, on the contrary, more or fewer of them are
innate, which so much exercised the mind of Locke, after a somewhat
summary fashion, in a note to the second section of the _Inquiry_:--

"It is probable that no more was meant by those who denied innate
ideas, than that all ideas were copies of our impressions; though
it must be confessed that the terms which they employed were not
chosen with such caution, nor so exactly defined, as to prevent all
mistakes about their doctrine. For what is meant by _innate_? If
innate be equivalent to natural, then all the perceptions and ideas
of the mind must be allowed to be innate or natural, in whatever
sense we take the latter word, whether in opposition to what is
uncommon, artificial, or miraculous. If by innate be meant
contemporary with our birth, the dispute seems to be frivolous; nor
is it worth while to inquire at what time thinking begins, whether
before, at, or after our birth. Again, the word _idea_ seems to be
commonly taken in a very loose sense by Locke and others, as
standing for any of our perceptions, our sensations and passions,
as well as thoughts. Now in this sense I should desire to know what
can be meant by asserting that self-love, or resentment of
injuries, or the passion between the sexes is not innate?

"But admitting these terms, _impressions_ and _ideas_, in the
sense above explained, and understanding by _innate_ what is