in the imagination.

The only difficulty, that can remain on this subject, must be with regard
to that custom, which so readily recalls every particular idea, for which
we may have occasion, and is excited by any word or sound, to which we
commonly annex it. The most proper method, in my opinion, of giving a
satisfactory explication of this act of the mind, is by producing other
instances, which are analogous to it, and other principles, which
facilitate its operation. To explain the ultimate causes of our mental
actions is impossible. It is sufficient, if we can give any satisfactory
account of them from experience and analogy.

First then I observe, that when we mention any great number, such as a
thousand, the mind has generally no adequate idea of it, but only a power
of producing such an idea, by its adequate idea of the decimals, under
which the number is comprehended. This imperfection, however, in our
ideas, is never felt in our reasonings; which seems to be an instance
parallel to the present one of universal ideas.

Secondly, we have several instances of habits, which may be revived by
one single word; as when a person, who has by rote any periods of a
discourse, or any number of verses, will be put in remembrance of the
whole, which he is at a loss to recollect, by that single word or
expression, with which they begin.

Thirdly, I believe every one, who examines the situation of his mind in
reasoning will agree with me, that we do not annex distinct and compleat
ideas to every term we make use of, and that in talking of government,
church, negotiation, conquest, we seldom spread out in our minds all the
simple ideas, of which these complex ones are composed. It is however