But the acquisition of these exalted attainments embraces the exercise of all the intellectual power on appropriate objects. The mental, like the corporeal powers, are various; they are differently organized and adapted to deal with objects of different natures; and, all require to be exercised judiciously, in order to be kept in a healthy tone. If any member of the body is disused, it will be deprived of its natural energy; if any faculty of the mind is disused, it will lose its natural strength. It is only when each faculty of mind and body is properly exercised that the health and vigor of the whole organism can be maintained. The physiological cause of the enervating effects of indolence, and the invigorating consequences of exercise, are found in those laws of the human organism, whereby the blood is increased in a member by exercise, and decreased by inertia, and a proportionable degree of strength imparted by one and, subtracted by the other. Now, the faculties employed in the process of meditation, comprehend but a small number of the mental powers; and if they are exclusively exercised, a superabundant volume of blood will be distributed to them, and they will absorb the aliment necessary for the subsistence of the others. The establishment of this inequality in the distribution of the blood will derange the harmonious condition of the cerebral organs; some will be overcharged, and either inflamed or constipated, and others impoverished or enervated. One class of the mental powers thus becoming over-excited, another class enfeebled, and a third paralyzed, the ideas which the mind, in this condition, is capable of elaborating, must necessarily be partial, defective, disjointed and grotesque; resembling those nightmares that flit in our sleep, or those monsters which are born without limbs, and marked with deformity and distortion. But when all the moral faculties are properly employed, they will all receive their appropriate nourishment and maintain their natural vigor. In consequence of a harmony, equality, unity and reciprocity of mental action, thus induced, all the powers will be preserved in healthy action--the perceptives in furnishing the mind with knowledge, memory in storing it up, order in classifying it, analogy in comparing it, judgment in deducing conclusions from it, taste in selecting what is most appropriate, fancy in adorning it; and all proceeding as naturally as the vital organ elaborates and vitalizes the blood, and the reproductive system transforms it into animal fluids and solids.