Morality has a basis of its own.
The moral philosopher, if asked, "Why should I act morally?" replies, "Because it is right for you to do so." If asked further, "Why is it right for me to do so?" he replies, "Because your conscience tells you that it is." If asked why conscience should be obeyed rather than passion, he replies, "Because it possesses greater authority, even if it has less power;" and in proof of this he points to the approval or disapproval which it stamps upon acts according to their character. Morality can be proved to be reasonable, apart from religion.
But it cannot be enforced. If a man denies that his conscience commands him to perform a moral action, the verdict of the general conscience of mankind may be quoted against him as contrary to that of his own, but he can repudiate the authority of that verdict so far as he is himself concerned. He can reasonably maintain that the general conscience may be misled by prejudice or superstition, and that his own conscience is more enlightened than that of the mass. In this manner the philosopher, or any one who regards himself as a philosopher, finds a way of evasion ready at hand.
With the masses, moral teaching, unaccompanied by religions sanction, is still less effectual. The general good of mankind, or the duty of obeying the highest principle of our nature, has never restrained, and never will restrain, the mass of mankind from yielding to the force of strong passion or desire.
In the present chapter we find the moral duties—those of the second table as much as the first—rested upon a religious basis. They are God's commands, whether that command be given by written precept or by an instinct engraven on man's heart. And because they are God's commands in both these ways, they are to be obeyed. Thus there is an appeal from man's mind to something higher than himself, to which man will submit. The effort to preserve morality in a nation without religious sanction and religious motive is like the attempt to keep alive the flame of a fire, when the fuel from which the flame is derived has been withdrawn. One generation may continue moral; the next will certainly be licentious. "I am the Lord" is a basis of morality which never fails.