316 NOTES. [BK. III.
supposed, in fact, never to be engaged upon what is practical as its office is contemplation, so that, "when dwelling upon what may be fearful, or otherwise, it does not, at once, suggest, flight or pursuit;" although, independently of its influence, "the heart or some other organ of the body may be accelerated or depressed." But in all this, as no allusion is made to a moving force, whether the motive be imagination or the stimulus of appetite, the inquiry may be said to be defective.
Note 2, p. 173. But to resume the more especial, &c.] Although these passages, which allude both to physical and moral causes of motion, are sufficiently obvious, yet, as they do not explain how locomotion is effected, they fail in the object of the inquiry; and then the motion concerned in nutrition, growth and decay, is almost in the same category, so to say, with that of progression. It may be mentioned that the "motion and progression of animals," "breathing and expiration," "sleep and watching," "youth and age," are special treatises, and probably composed for the elucidation of this particular work upon "life." The comparison between the intemperate man who, although rational, acts against his reason, and the physician who, although versed in medical science, does not cure, seems to exemplify the adage, that to advise is one thing, to do, another; or to confirm the solemn words of Johnson, "that teachers of morality discourse like angels, but they live like men."