xical, that ideas can exist, and not be attended to;
but all our perceptions are ideas excited by irritation, and succeeded by
sensation. Now when these ideas excited by irritation give us neither
pleasure nor pain, we cease to attend to them. Thus whilst I am walking
through that grove before my window, I do not run against the trees or the
benches, though my thoughts are strenuously exerted on some other object.
This leads us to a distinct knowledge of irritative ideas, for the idea of
the tree or bench, which I avoid, exists on my retina, and induces by
association the action of certain locomotive muscles; though neither itself
nor the actions of those muscles engage my attention.

Thus whilst we are conversing on this subject, the tone, note, and
articulation of every individual word forms its correspondent irritative
idea on the organ of hearing; but we only attend to the associated ideas,
that are attached by habit to these irritative ones, and are succeeded by
sensation; thus when we read the words "PRINTING-PRESS" we do not attend to
the shape, size, or existence of the letters which compose these words,
though each of them excites a correspondent irritative motion of our organ
of vision, but they introduce by association our idea of the most useful of
modern inventions; the capacious reservoir of human knowledge, whose
branching streams diffuse sciences, arts, and morality, through all nations
and all ages.

* * * * *

SECT. VIII.

OF SENSITIVE MOTIONS.

I. 1. _Sensitive muscular motions were originally excited into action
by irritation._ 2. _And sensitive sensual motions, ideas of
imagination, dreams._ II. 1. _Sensitive muscular motions are
occasionally obedient to volition._ 2. _And sensitive sensual motions._
III. 1. _Other muscular motions are associated with the sensitive
ones._ 2. _And other sensual motions._

I. 1. Many of the motions of our muscles, that are excited into action by
irritation, are at the same time accompanied with painful or pleasurable
sensations; and at length become by habit causable by the sensations. Thus
the motions of the sphincters of the bladder and anus were originally
excited into action by irritation; for young children give no attention to
these evacuations; but as soon as they become sensible of the inconvenience
of obeying these irritations, they suffer the water or excrement to
accumulate, till it disagreeably a