necessary
for those purposes become associated by habit, and gain a great adroitness
of action by these early repetitions: so the motions of the abdominal
muscles, which were originally brought into concurrent action, with the
protrusive motion of the rectum or bladder by sensation, become so
conjoined with them by habit, that they not only easily obey these
sensations occasioned by the stimulus of the excrement and urine, but are
brought into violent and unrestrainable action in the strangury and
tenesmus. This kind of connection we shall term sensitive association.

2. So many of our ideas, that have been excited together or in succession
by our sensations, gain synchronous or successive associations, that are
sometimes indissoluble but with life. Hence the idea of an inhuman or
dishonourable action perpetually calls up before us the idea of the wretch
that was guilty of it. And hence those unconquerable antipathies are
formed, which some people have to the sight of peculiar kinds of food, of
which in their infancy they have eaten to excess or by constraint.

III. 1. In learning any mechanic art, as music, dancing, or the use of the
sword, we teach many of our muscles to act together or in succession by
repeated voluntary efforts; which by habit become formed into tribes or
trains of association, and serve all our purposes with great facility, and
in some instances acquire an indissoluble union. These motions are
gradually formed into a habit of acting together by a multitude of
repetitions, whilst they are yet separately causable by the will, as is
evident from the long time that is taken up by children in learning to walk
and to speak; and is experienced by every one, when he first attempts to
skate upon the ice or to swim: these we shall term voluntary associations.

2. All these muscular movements, when they are thus associated into tribes
or trains, become afterwards not only obedient to volition, but to the
sensations and irritations; and the same movement composes a part of many
different tribes or trains of motion. Thus a single muscle, when it acts in
consort with its neighbours on one side, assists to move the limb in one
direction; and in another, when, it acts with those in its neighbourhood on
the other side; and in other directions, when it acts separately or jointly
with those that lie immediately under or above it; and all these with equal
facility after their associations have been well established.