In the face of bad example, the best of precepts are of but little avail.

The example is followed, not the precepts.

Indeed, precept at variance with practice is worse than useless, inasmuch as it only serves to teach the most cowardly of vices--hypocrisy.

Even children are judges of consistency, and the lessons of the parent who says one thing and does the opposite, are quickly seen through.

The teaching of the friar was not worth much, who preached the virtue of honesty with a stolen goose in his sleeve.
By imitation of acts, the character becomes slowly and imperceptibly, but at length decidedly formed.