As an instance of the advantage which a philosophical traveller has over an unprepared one, look at the difference which will enter into a man's judgment of nations, according as he carries about with him the vague popular notion of a Moral Sense, or has investigated the laws under which feelings of right and wrong grow up in all men. It is worth while to dwell a little on this important point. Most persons who take no great pains to think for themselves, have a notion that every human being has feelings, or a conscience, born with him, by which he knows, if he will only attend to it, exactly what is right and wrong; and that, as right and wrong are fixed and immutable, all ought to agree as to what is sin and virtue in every case. Now, mankind are, and always have been, so far from agreeing as to right and wrong, that it is necessary to account in some manner for the wide differences in various ages, and among various nations. A great diversity of doctrines has been put forth for the purpose of lessening the difficulty; but they all leave certain portions of the race under the condemnation or compassion of the rest for their error, blindness, or sin. Moreover, no doctrines yet invented have accounted for some total revolutions in the ideas of right and wrong, which have occurred in the course of ages. A person who takes for granted that there is an universal Moral Sense among men, as unchanging as he who bestowed it, cannot reasonably explain how it was that those men were once esteemed the most virtuous who killed the most enemies in battle, while now it is considered far more noble to save life than to destroy it. They cannot but wonder how it was that it was once thought a great shame to live in misery, and an honour to commit suicide; while now the wisest and best men think exactly the reverse. And, with regard to the present age, it must puzzle men who suppose that all ought to think alike on moral subjects, that there are parts of the world where mothers believe it a duty to drown their children, and that eastern potentates openly deride the king of England for having only one wife instead of one hundred. There is no avoiding illiberality, under this belief,--as the philosopher understands illiberality. There is no avoiding the conclusion that the people who practice infanticide and polygamy are desperately wicked; and that minor differences of conduct are, abroad as at home, so many sins.