One man goes directly into the gratification of it, without any consideration. Another, who feels the same desire, considers the influence which the indulgence would be likely to have on his health, interest, or reputation.--This may be considered as simply an exercise of judgment, combined with a certain operation of self-love. A third views the aspect of the deed purely as a question of moral responsibility,--and, if he sees cause, decides against it on this ground alone;--though he should perceive that it might be gratified without any danger to his health, interest, or reputation, or even that it might contribute to his advantage. We have thus presented to us three characters;--one who acts upon the high and pure ground of moral principle;--one who acts from motives of a more contracted and personal nature, though, in certain instances, his conduct may be the same;--and one who goes straight forward to the gratification of a ruling desire or governing propensity, without attending to motives of either class. The first is a uniform character, on whose conduct we depend in any given circumstances, with a confidence similar to that with which we rely on the operation of physical agents. For we know the uniform tendencies of the motives or moral causes by which he is habitually influenced, and we know his moral temperament. We have nearly the same kind of knowledge respecting him, which we have of the tendencies of chemical agents towards each other, and which enables us with perfect confidence to foretel their actions. The third has also a uniformity of conduct, though of a very different kind. We know, likewise, his moral condition, and, to predict his conduct, we require only to learn the particular inducements or temptations to which he is exposed in a given instance. The second we cannot rely or calculate upon; for we have not the means of tracing the conflicting views by which he may be influenced in a particular case, or the principle on which he may ultimately decide between them. They involve the strength of the inclination,--and the degree of power exerted over it by the class of personal or selfish motives by which he is influenced.--In regard to various instances of ill-regulated desire, we must add his hope of evading detection,--as on this depends, in a great measure, the kind of evils dreaded by him in reference to the indulgence. These taken together imply a complicated moral calculation, of which it is impossible for another man to trace the result. There cannot be an inquiry of more intense interest than to investigate the causes in which originate the differences among these three characters; or, in other words, the principles on which we can explain the fact, that the will of individuals may be influenced so differently with the same motives before them. These appear to be referable to three heads,--Knowledge,--Attention,--and Moral Habits.