Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

THE ASSOCIATION OF IDEAS. 167
the mind possesses over the train of its thoughts, the most
obvious is its power of singling out any one of them at pleasure;
of detaining it; and of making it a particular object of attention. By doing so, we not only stop the succession that would
otherwise take place; but, in consequence of our bringing to
view the less obvious relations among our ideas, we frequently
divert the current of our thoughts into a new channel. If, for
example, when I am indolent and inactive, the name of Sir
Isaac Newton accidentally occur to me, it will perhaps suggest,
one after another, the names of some other eminent mathematicians and astronomers, or some of his illustrious contemporaries
and friends: and a number of them may pass in review before
me, without engaging my curiosity in any considerable degree.
In a different state of mind, the name of Newton will lead my
thoughts to the principal incidents of his life, and the more
striking features of his character: or, if my mind be ardent and
vigorous, will lead my attention to the sublime discoveries he
made; and gradually engage me in some philosophical investigation. To every object, there are others which bear obvious
and striking relations; and others, also, whose relation to it
does not readily occur to us, unless we dwell upon it for some
time, and place it before us in different points of view.
But the principal power we possess over the train of our ideas,
is founded on the i7nfluence which our habits of thinking have on
the laws of association; an influence which is so great, that we
may often form a pretty shrewd judgment concerning a man's
prevailing turn of thought, from the transitions he makes in
conversation or in writing. It is well known, too, that by means
of habit, a particular associating principle may be strengthened
to such a degree, as to give us a command of all the different
ideas in our mind, which have a certain relation to each other;
so that, when any one of the class occurs to us, we have almost
a certainty that it will suggest the rest. What confidence in his
own powers must a speaker possess, when he rises without premeditation, in a popular assembly, to amuse his audience with a
lively or a humorous speech! Such a confidence, it is evident,