A child who can not understand a single complete sentence, or speak an intelligible phrase, will sit and listen with long-continued delight to the simple enunciation of words, each one of which presents a picture to his mind of a dog, a cat, a cow, a horse, a whip, a ride, and many other objects and scenes that have given pleasure in the past; while the single words, without any sentences, bring back, not only vivid conceptions of these objects, but a part of the enjoyment with which they have been connected. Then, as years pass by, the intellect more and more administers pleasure, while the reasoning powers are developed, the taste cultivated, the imagination exercised, the judgment employed, and the memory stored with treasures for future enjoyment. In the proper and temperate use of the intellectual powers, there is a constant succession of placid satisfaction, or of agreeable and often of delightful emotions, while no one of these faculties is productive of pain except in violating the laws of the mental constitution. _The Susceptibilities._ In regard to the second general class of mental powers--_the susceptibilities_--the first particular to be noticed is the ceaseless and all-pervading _desire to gain happiness and escape pain_. This is the mainspring of all voluntary activity; for no act of volition will take place till some good is presented to gain, or some evil to shun. At the same time, as has been shown, the desire to escape evil is more potent and effective than the desire for good. Thousands of minds that rest in passive listlessness, when there is nothing to stimulate but hope of enjoyment, will exert every physical and mental power to escape impending evil. The seasons of long-continued prosperity in nations always tend to a deterioration of intellect and manhood. It is in seasons of danger alone that fear wakes up the highest energies, and draws forth the heroes of the race. Mind, then, is an existence having the power of that self-originating action of _choice_ which constitutes free agency, while this power can only be exercised when desires are excited to gain happiness or to escape pain. This surely is the highest possible evidence that its Author _intended_ mind should thus act. But a mind may act to secure happiness and avoid pain to itself, and yet may gain only very low grades of enjoyment, while much higher are within reach of its faculties. So, also, it may act to gain happiness for itself as the chief end in such ways as to prevent or destroy the happiness of others around. In reference to this, we find those susceptibilities which raise man to the dignity of a moral being. In the first place, there is that _impression of the great design_ of the Creator existing in every mind, either as a result of constitution or of training, or of both united, which results in a feeling that whatever lessens or destroys happiness is unfit and contrary to the system of things.