action_. Habit differs from _disposition_, as disposition is a quality
easily changed. Thus one in a good humour is in a _disposition_ to be
kind. Habit is a part of character: disposition is a passing fit.
Again, habit differs from faculty, or power: as power enables one to
act; but habit, presupposing power, renders action easy and
expeditious, and reliable to come at call. We have a power to move our
limbs, but a habit to walk or ride or swim. Habit then is the
determinant of power. One and the same power works well or ill, but
not one and the same habit.

2. A power that has only one way of working, set and fixed, is not
susceptible of habit. Such powers are the forces of inanimate nature,
as gravitation and electricity. A thing does not gravitate better for
gravitating often. The moon does not obey the earth more readily
to-day than she did in the days of Ptolemy, or of the Chaldean sages.
Some specious claim to habit might be set up on behalf of electricity
and magnetism. A glass rod rubbed at frequent intervals for six
months, is a different instrument from what it would have been, if
left all that time idle in a drawer. Then there are such cases as the
gradual magnetising of an iron bar. Still we cannot speak of
electrical habits, or magnetic habits, not at least in things without
life, because there is no will there to control the exercise of the
quality. As well might we speak of a "tumbledown" habit in a row of
houses, brought on by locomotives running underneath their
foundations. It is but a case of an accumulation of small effects,
inducing gradually a new molecular arrangement, so that the old powers
act under new material conditions. But habit is a thing of life, an
appurtenance of will, not of course independent of material conditions
and structural alterations, in so far forth as a living and volitional
is also a material agent, but essentially usable _at will_, and