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 brought into play and controlled in its operation by free choice. Therefore a habit that works almost automatically has less of the character of a true habit, and passes rather out of morality into the region of physics. Again, bad habits, vices to which a man is become a slave against his better judgment, are less properly called habits than virtues are; for such evil habits do not so much attend on volition (albeit volition has created them) as drag the will in their wake. For the like reason, habit is less properly predicable of brute animals than of men: for brutes have no intelligent will to govern their habits. The highest brutes are most susceptible of habit. They are most like men in being most educable. And, of human progeny, some take up habits, in the best and completest sense of the term, more readily than others. They are better subjects for education: education being nothing else than the formation of habits. 3. Knowledge consists of intellectual habits. But the habits of most consequence to the moralist lie in the will, and in the sensitive appetite as amenable to the control of the will. In this category come the virtues, in the ordinary sense of that name, and secondarily the vices.