The Cobbler turned Physician

The Fables of Phædrus
A bungling Cobbler, broken down by want, having begun to practise physic in a strange place, and selling his antidoteI.15 under a feigned name, gained some reputation for himself by his delusive speeches.
Upon this, the King of the city, who lay ill, being afflicted with a severe malady, asked for a cup, for the purpose of trying him; and then pouring water into it, and pretending that he was mixing poison with the fellow’s antidote, ordered him to drink it off, in consideration of a stated reward. Through fear of death, the cobbler then confessed that not by any skill in the medical art, but through the stupidity of the public, he had gained his reputation. The King, having summoned a council, thus remarked: “What think you of the extent of your madness, when you do not hesitate to trust your livesI.16 to one to whom no one would trust his feet to be fitted with shoes?”
This, I should say with good reason, is aimed at those through whose folly impudence makes a profit.