And he must be able to do this, if his system is worth anything; and in promulgating his system he professes that he can do it.

The physician's work is to heal the sick; his skill must not end in explaining his own health.

It is clear that if a morality is incapable of being preached, it is useless to say that it is worthy of being practised.

The statement will be meaningless, except to those for whom it is superfluous.

It is therefore essential to the moral end that in some way or other it be generally presentable, so that its excellence shall appeal to some common sense in man.