We distinguish in man a double nature, _body_ and _soul_; and in the soul itself two parts, one superior, one inferior; one more particularly deserving of the name of soul, the other more carnal, more material, if one may say so, which comes nearer the body. In one class we have _intelligence_, _sentiments_, _will_; in the other, _senses_, _appetites_, _passions_. Now, that which distinguishes man from the lower animal is the power to rise above the senses, appetites, and passions, and to be capable of thinking, loving, and willing. Thus, moral good consists in preferring what there is best in us to what there is least good; the goods of the soul to the goods of the body; the dignity of human nature to the servitude of animal passions; the noble affections of the heart to the inclinations of a vile selfishness. In one word, moral good consists in man becoming truly man--that is to say, "A free will, guided by the heart and enlightened by reason." Moral good takes different names, according to the relations under which we consider it. For instance, when we consider it as having for its special object the individual man in relation with himself, good becomes what is properly called the _honest_, and has for its prime object personal dignity. In its relation with other men, good takes the name of the _just_, and has for its special object the happiness of others. It consists either in not doing to others what we should not wish they should do to us, or in doing to others as we should ourselves wish to be done by. Finally, in its relation to God, the good is called piety or saintliness, and consists in rendering to the Father of men and of the universe what is his due. =9. Duty.=--Thus, the _honest_, the _just_, and the _pious_ are the different names which moral good takes in its relations to ourselves, to other men, or to God. Moral good, under these different forms, presents itself always in the same character, namely, imposing on us the obligation to do it as soon as we recognize it, and that, too, without regard to consequences and whatever be our inclinations to the contrary. Thus, we should tell the truth even though it injures us; we should respect the property of others, though it be necessary to our existence; finally, we should even sacrifice, if necessary, our life for the family and the country. This law, which prescribes to us the doing right for its own sake, is what is called _moral law_ or the _law of duty_. It is a sort of constraint, but a _moral constraint_, and is distinguished from _physical_ constraint by the fact that the latter is dictated by fate and is irresistible, whilst the constraint of duty imposes itself upon our reason without violating our liberty. This kind of necessity, which commands reason alone without constraining the will, is moral _obligation_.