But how shall the sentiment of filial gratitude express itself? Gratitude is usually displayed by a return of the kindness received. But the kindness which we receive from parents is such that we can never repay it. It is of the nature of a debt which we can never hope fully to cancel. We can do this much--when our parents grow old, we can care for them, and smooth the last steps that lead to the grave. And when we ourselves have grown to manhood and womanhood, and have in turn become parents, we can bestow upon our own offspring the same studious and intelligent care which our parents, according to the light they had, bestowed on us, and thus ideally repay them by doing for others what they did for us. But this is a point which concerns only adults. As for young children, they can show their gratitude in part by slight services, delicacies of behavior, the chief value of which consists in the sentiment that inspires them, but principally by a willing acceptance of parental guidance, and by earnest efforts in the direction of their own intellectual and moral improvement. There is no love so unselfish as parental love. There is nothing which true parents have more at heart than the highest welfare of their children. There is no way in which a child can please father and mother better than by doing that which is for its own highest good. The child's progress in knowledge and in moral excellence are to every parent the most acceptable tokens of filial gratitude. And this leads me to an important point, to which reference has already been made. It has been stated that each period of life has its distinct set of duties; furthermore, that in each period there is one paramount duty, around which the others may be grouped; and, lastly, that at each successive stage it is important to reach backward and to bring the ethical system of the preceding period into harmony with the new system. Of this last point we are now in a position to give a simple illustration. The paramount duty of the school period is to acquire knowledge; the paramount duty of the previous period is to reverence parents. But, as has just been shown, reverence toward parents at this stage is best exhibited by conscientious study, and thus the two systems are merged into one.[17] THE FRATERNAL DUTIES.