There is, of course, a process of constant Interaction going on between the two elements in the constitution of moral sentiment which I have been attempting to describe.  The circumstances, opinions, and feelings of the society of which he is a member, must necessarily contribute to determine the opinions and feelings, the character and aims, of the moralist or the reformer.  In turn, the moralist or reformer modifies, corrects, and elevates the current moral sentiment of those who are brought within the influence of his work.  And this result is usually a permanent one.  When the average moral sentiment on a particular point of conduct has been consciously raised, and the change is fully realised, it seldom happens that it afterwards recedes, though the automatic or semi-conscious adaptations of society to new needs and circumstances, when regarded from a more general point of view, are not infrequently found to be regressive as well as progressive.  Thus, though we may imagine the distinctions between the different classes of society becoming more numerous or more accentuated (as I believe to have actually occurred in England during the present century), or the evasion of taxation becoming more general than it at present is, we can hardly conceive a recurrence to slavery, or a needless increase in the severity of punishments, or a revival of the hard-drinking habits of the last century.  When society is fully aware of its moral gains, it is not likely knowingly to surrender them.  Hence, allowing for occasional oscillations and for possible exceptions in certain departments of conduct, morality, as a whole, almost necessarily advances with the general progress of intelligence.

It is not altogether easy to adjust the respective claims of society at large and of the individual thinker in the constitution of moral theory, or, in other words, to determine the limits within which the speculative moralist may legitimately endeavour to reform the existing moral sentiment.  It is plain that it must be open to the moralist, and, in fact, to every intelligent citizen, to criticize the current morality, or else moral progress, even if it took place at all, would, on many points of conduct, be exceedingly slow.  But, on the other hand, it is equally plain that a constant discussion of the accepted rules of conduct would weaken the moral sentiment, lessen the sense of obligation, and suggest a general uncertainty as to the validity of the maxims which, in their relations to one another, men usually take for granted.  Hence, though it would be almost fatal to moral progress to discourage speculation on moral topics, the moralist must always bear in mind that his task is one which is not lightly to be undertaken, and that, with an exception to be noticed presently, the presumption should always be in favour of existing rules of conduct.  If for no other reason, this presumption ought to be made on the practical ground that a disturbance of the moral sentiment on one point is likely to weaken