The effect of use and wont in the moral sphere could hardly be expressed more forcibly, and Jeremiah's comparison has become a proverb. Custom binds us all in every department of life; it is only by enlisting this strange influence upon the side of virtue, that we become virtuous. Neither virtue nor vice can be pronounced perfect, until the habit of either has become fixed and invariable. It is the tendency of habitual action of any kind to become automatic; and it is certain that sin may attain such a mastery over the active powers of a man that its indulgence may become almost an unconscious exercise of his will, and quite a matter of course. But this fearful result of evil habits does not excuse them at the bar of common sense, much less at the tribunal of God. The inveterate sinner, the man totally devoid of scruple, whose conscience is, as it were, "seared with a hot iron," is not on that account excused by the common judgment of his kind; the feeling he excites is not forbearance, but abhorrence; he is regarded not as a poor victim of circumstances over which he has no control, but as a monster of iniquity. And justly so; for if he has lost control of his passions, if he is no longer master of himself, but the slave of vice, he is responsible for the long course of self-indulgence which has made him what he is. The prophet's comparison cannot be applied in support of a doctrine of immoral fatalism. The very fact that he makes use of it, implies that he did not intend it to be understood in such a sense. "_Will a Cushite change his skin, or a leopard his spots? Ye also_--supposing such a change as that--_will be able to do good, O ye that are taught_--trained, accustomed--_to do evil_!" (perhaps the preferable rendering). Not only must we abstain from treating a rhetorical figure as a colourless and rigorous proposition of mathematical science; not only must we allow for the irony and the exaggeration of the preacher: we must also remember his object, which is, if possible, to shock his hearers into a sense of their condition, and to awaken remorse and repentance even at the eleventh hour. His last words (ver. 27) prove that he did not believe this result, improbable as it was, to be altogether impossible. Unless some sense of sin had survived in their hearts, unless the terms, "good" and "evil," had still retained a meaning for his countrymen, Jeremiah would hardly have laboured still so strenuously to convince them of their sin.