In this concluding section of the Enquiry, Hume attempts a further justification of the theory of morals which has been presented in the earlier sections of the book. He begins by calling attention to the fact that what he has said concerning the origin and existence of moral sentiments appears to be so obvious that it is strange indeed that anyone should have felt it necessary to elaborate any argument in defense of it. It would seem that common sense alone would be sufficient to make it clear to any fair-minded person that the principles of morality are all based on the approval of that which is pleasant and useful either to ourselves or to others and the disapproval of that which is contrary to these ends. In fact, we are told that this is sufficient for the great masses of ordinary folk, and had it not been for the confusion and lack of clear understanding on the part of certain learned philosophers and theologians, there would have been no occasion for writing this treatise on morals.
However, confusion on the part of those who profess to be experts in the field leads to doubts and uncertainties among their followers, and it seems to be quite in order to attempt a clarification of the issues involved. So long as people judge matters of this kind by their natural and unprejudiced reason, they will be able to see morality in the light in which he has presented it. It is only when their minds have been corrupted by superstition and false religious notions that they are led astray. Under influences of this kind, they have set forth conceptions of the nature of morality that are not only ill-founded but in many instances have led to practices which are detrimental to human welfare.
Hume is especially critical of a long list of practices which have been fostered in the name of morality but which in his judgment ought to be regarded as vices rather than virtues. The list includes such items as celibacy, fasting, penance, mortification of the flesh, self-denial, humility, silence, solitude, and what he calls "the whole train of monkish virtues." Obviously, he does not mean that any participation in these practices should be forbidden under any and all circumstances. Rather, he means that these practices in the sense in which they have been regarded as virtues by certain theologians and other leaders of the Church should be rejected.
His opposition to them is based on the fact that they make no positive contribution toward the fulfillment of human needs. They do not advance a person's fortune. They do not make an individual a more valuable member of society. They do not qualify him for the entertainment of others, and neither do they increase his own capacity for self-enjoyment. Because they are neither agreeable nor useful in satisfying the needs of ourselves or of other people, it is a mistake to regard them as moral virtues which ought to be cultivated.
The fact that Hume places so much emphasis on the matter of approval or disapproval as a criterion of morality has led some of his critics to charge that his doctrine is essentially a selfish one. However, a careful reading of the Enquiry shows beyond any doubt that this charge is an ill-founded one. Against those philosophers who have insisted that all human actions are selfishly motivated, Hume calls attention to the fact that there is present in all human beings a kind of humanitarian sentiment which naturally approves of that which is useful and serviceable to humanity and looks with disfavor on all those actions that are dangerous and pernicious. This does not mean that selfishness is excluded from human nature. It is very much a part of human nature and in many instances is so much stronger than any altruistic element that the latter may be completely overshadowed by the former.
Concerning degrees of selfishness and of benevolence, we have no exact method of measurement, and it is idle to speculate about them. Nevertheless, it is sufficient to counteract the position of those who hold that the principles of morality are in every instance the expression of a purely selfish concern, if it can be shown that there is some spark of friendship for all human kind. The amount may be small, so small in fact that it is insufficient to move even a hand or a finger, but still it is enough to exercise an important influence on the mind. It is this influence that causes us, when other factors are equal, to "have a cool preference for what is useful and serviceable to mankind above what is pernicious and dangerous."
From these considerations, it follows that the principles of morality are not derived from self-love alone. If they were, we would find no general area of agreement concerning the type of actions which are approved, and this is contrary to what actually is the case. Self-love is always directed toward the achievement of each individual's personal ambitions. We know that what is one person's ambitions is not that of another, and so long as each one is pursuing purely selfish aims, there is bound to be no end of conflict. The areas of agreement in the field of morals are altogether too great to be accounted for in this manner. They can be understood only on the basis of some common element which can be found in human nature.
This is evidently what Hume means when he states that the humanity of one person is the same as the humanity of every other person. It is true that this sense of humanity is not as strong in some persons as it is in others, and its manifestation is often present in varying degrees. Nevertheless, the fact that it exists to some extent in all normal human beings is sufficient to explain that sense of approval which all people feel toward those acts of justice and benevolence which are beneficial either to ourselves or to others. What gains the approval of one person by touching his sense of humanity will also win the respect and admiration of all humanity. The natural desire for fame and a good reputation among one's fellow humans helps to keep alive this humane element in all persons.