Chapter III. is 'On the influence and authority of Conscience;' another long chapter, occupied more with moral reflections of a practical kind than with the following out of the analysis of our moral sentiment. Conceding that the testimony of the supposed impartial spectator does not of itself always support a man, he yet asserts its influence to be great, and that by it alone we can see what relates to ourselves in the proper shape and dimensions. It is only in this way that we can prefer the interest of many to the interest of one; the interest of others to our own. To fortify us in this hard lesson two different schemes have been proposed; one to increase our feelings for others, the other to diminish our feelings for ourselves. The first is prescribed by the whining and melancholy moralists, who will never allow us to be happy, because at every moment many of our fellow-beings are in misery. The second is the doctrine of the Stoics, who annihilate self-interest in favour of the vast commonwealth of nature; on that the author bestows a lengthened comment and correction, founded on his theory of regulating the manifestations of joy or grief by the light of the impartial judge. He gives his own panacea for human misery, namely, the power of nature to accommodate men to their permanent situation, and to restore tranquillity, which is the one secret of happiness. Chapter IV. handles Self-Deceit, and the Origin and Use of General Rules. The interference of our passions is the great obstacle to our holding towards ourselves the position of an impartial spectator. Prom this notorious fact the author deduces an argument against a special moral faculty, or moral sense; he says that if we had such a faculty, it would surely judge our own passions, which are the most clearly laid open to it, more correctly than the passions of others. To correct our self-partiality and self-deceit is the use of general rules. Our repeated observations on the tendency of particular acts, teach us what is fit to be done generally; and our conviction of the propriety of the general rules is a powerful motive for applying them to our own case. It is a mistake to suppose, as some have done, that rules precede experience; on the contrary, they are formed by finding from experience that all actions of a certain kind, in certain circumstances, are approved of. When established, we appeal to them as standards of judgment in right and wrong, but they are not the original judgments of mankind, nor the ultimate foundations of moral sentiment.