But then, as a counterbalancing result, it is seen that these losses to individuals are made available to the protection and improvement of the race, and seem indispensable to it; for it is the example of the evils suffered by wrong-doers that is constantly exercising a preservative influence to deter others from similar courses. Thus good is constantly educed from ill, even in the most melancholy cases. We have seen that it is the desire of good and fear of evil that is the motive power in causing all mental action, and we have the history of man to teach us also what kinds of motives prove the most effective in securing that obedience to law which is the only way to true and perfect happiness. Our only mode of learning the nature of a thing is to observe how it acts and is acted upon. This is as true of mind as it is of material things. What, then, has the experience of our race taught as to the nature of mind in reference to the kinds and relative influence of motive that secure obedience to law? In the first place, then, we learn that _fear of evil is indispensable_. As soon as children in the family, or adults in society, find that no harm comes from gratifying their desires, all restraint is removed. So strong is this necessity, that when natural penalties seem uncertain or far off, parents and civil rulers find it imperative to add those which are more immediate and discernible. But with this we learn that fear alone is not a healthful stimulus. Children and slaves who have no motives to action but fear of penalties are never so successfully led to obedience as when other more agreeable influences are combined. A mind that is constantly goaded to action by fear of evil becomes torpid, or irritable, or despairing, or all together. The hope of good, or rewards, then, are as indispensable to secure obedience to law as penalties. The proper balancing of the motives of fear of evil and hope of good is the grand art of controlling mind, both as it respects individuals and communities. In reference to those motives that are pleasurable, there are two classes which it is very important to recognize. The first class are those sources of enjoyment which are sought for the gratification of self without any reference to another. Of this class are the pleasures of the senses, the enjoyment of acquiring knowledge, the exercise of power, the pleasures of taste, and others that need not here be specified. The second class are those in which the enjoyment is secured by producing happiness for others, and is sought solely in reference to the enjoyment of another. The most decided illustration of this kind is that of a mother who is providing for her offspring. This and all true love has, as its distinctive feature, the pleasure found in conferring happiness on the beloved object. Gratitude, also, has for its main element the desire to make some returns of enjoyment to one who has conferred a favor.