Wisdom from Gregory the Great

"Thus is was that Nathan the Prophet, come to chide the king, to all appearance asked his judgment in the case of a poor man against a rich man.  The king first was to deliver judgment and then to hear that he was the culprit.  Thus he was completely unable to gainsay the just sentence which he had personally delivered against himself.  Therefore, the holy man, considering both the sinner and the king, aimed in that wonderful manner at convicting a bold culprit first by his own admission, and then cut him by his rebuke.  For a short while he concealed the person whom he was aiming at, and then at once struck him when he had convicted him.  His stroke would, perhaps, have had less force, if he had chosen to castigate the sin directly the moment he began to speak; but by beginning with a similitude, he sharpened the rebuke which he was concealing.  He came like a physician to a sick man, saw that his wound had to be incised, but was in doubt about the endurance of the patient.  He, therefore, concealed the surgeon's knife under his coat, but drawing it out suddenly, pierced the wound, that the sick man might feel the knife before he saw it, for if he had first seen it, he might have refused to feel it."

- St. Gregory the Great, 'Pastoral Care' Part III, Chapter 2.