possesses a
memory so good, that if he has only once observed a natural object, a
second inspection does not show him something that he has forgotten.
Almost all, if not all, our memories are therefore sketches, rather than
portraits, of the originals--the salient features are obvious, while the
subordinate characters are obscure or unrepresented.

Now, when several complex impressions which are more or less different
from one another--let us say that out of ten impressions in each, six
are the same in all, and four are different from all the rest--are
successively presented to the mind, it is easy to see what must be the
nature of the result. The repetition of the six similar impressions will
strengthen the six corresponding elements of the complex idea, which
will therefore acquire greater vividness; while the four differing
impressions of each will not only acquire no greater strength than they
had at first, but, in accordance with the law of association, they will
all tend to appear at once, and will thus neutralise one another.

This mental operation may be rendered comprehensible by considering what
takes place in the formation of compound photographs--when the images of
the faces of six sitters, for example, are each received on the same
photographic plate, for a sixth of the time requisite to take one
portrait. The final result is that all those points in which the six
faces agree are brought out strongly, while all those in which they
differ are left vague; and thus what may be termed a _generic_ portrait
of the six, in contradistinction to a _specific_ portrait of any one, is
produced.

Thus our ideas of single complex impressions are incomplete in one way,
and those of numerous, more or less similar, complex impressions are
incomplete in another way; that is to say, they are _generic_, not
_specific_. And hence it follows, that our ideas of the impressions in
question are not, in the strict sense of the word, copies of those
impressions; while, at the same time, they may exist in the mind
independently of language.

The generic ideas which are formed from several similar, but not
identical, complex experiences are what are commonly called _abstract_
or _general_ ideas; and Berkeley endeavoured to prove that all general
ideas are nothing but particular ideas annexed to a certain term, which
gives them a more extensive signification, and makes them recall, upon
occasion, other individuals which are similar