It is this mistake that is the essence and cause of immorality; it is this mistake that mankind is ever inclined to make, and it is only because of this inclination that any moral system is of any general value.
Were we all naturally inclined to morality, the analysis of it, it is true, might have great speculative interest; but a moral system would not be needed as it is for a great practical purpose.

The law, as we all know, has arisen because of transgressions, and the moralist has to meddle with human nature mainly because it is inconstant and corrupted.
It is a wild horse that has not so much to be broken, once for all, as to be driven and reined in perpetually.

And the art of the moralist is, by opening the mind's eye to the true end of life, to make us sharply conscious of what we lose by losing it.

And the men to whom we shall chiefly want to present this end are not men, let us remember, who desire to see it, or who will seek for it of their own accord, but men who are turned away from it, and on whose sight it must be thrust.

It is not the righteous but the sinners that have to be called to repentance.
And not this only: not only must the end in question be thus presentable, but when presented it must be able to stand the inveterate criticism of those who fear being allured by it, who are content as they are, and have no wish to be made discontented.