The mode by which the mind succeeds in forming such a habit seems to be by that implanted principle which makes ideas that are most in consonance with the leading desire of the mind become vivid and distinct, while those that are less interesting fade away. Now no person desires to witness pain except from the hope of relieving it, unless it be that, in anger, the mind is sometimes gratified with the infliction of suffering. But, in ordinary cases, the sight of suffering is avoided except where relief can be administered. In such cases, the desire of administering relief becomes the leading one, so that the mind is turned off from the view of the suffering to dwell on conceptions of modes of relief. Thus the surgeon and physician gradually form such habits that the sight of pain and suffering lead the mind to the conception of modes of relief, whereas a mind not thus interested dwells on the more painful ideas.
The habits of life are all formed either from the desire to secure happiness or to avoid pain, and the _fear of suffering_ is found to be a much more powerful principle than the _desire of happiness_. The soul flies from pain with all its energies, even when it will be inert at the sight of promised joy. As an illustration of this, let a person be fully convinced that the gift of two new senses would confer as great an additional amount of enjoyment as is now secured by the eye and ear, and the promise of this future good would not stimulate with half the energy that would be caused by the threat of instant and entire blindness and deafness.
If, then, the mind is stimulated to form good habits and to avoid the formation of evil ones most powerfully by painful emotions, when their legitimate object is not effected they continually decrease in vividness, and the designed benefit is lost. If a man is placed in circumstances of danger, and fear leads to habits of caution and carefulness, the object of exciting this emotion is accomplished, and the diminution of it is attended with no evil. But if fear is continually excited, and no such habits are formed, then the susceptibility is lessened, while the good to be secured by it is lost. So, also, with emotions of sympathy. If we witness pain and suffering, and it induces habits of active devotion to the good of those who suffer, the diminution of the susceptibility is a blessing and no evil. But if we simply indulge emotions, and do not form the habits they were intended to secure, the power of sympathy is weakened, and the designed benefit is lost. Thus, again, with shame: if this painful emotion does not lead us to form habits of honor and rectitude, it is continually weakened by repetition, and the object for which it was bestowed is not secured. And so with remorse: if this emotion is awakened without leading to habits of benevolence and virtue, it constantly decays in power, and the good it would have secured is for ever lost.