Johnson spent several years writing his Dictionary of the English language. It was a big job. While he was writing it he could not be earning money, so he needed a patron (someone who would sponsor him by giving him money, and in return the dictionary would be dedicated to him). An important man called Lord Chesterfield said to Johnson that he would be his patron. But he never gave him any money, and Johnson never heard anything more from him, until the dictionary was ready. Then Lord Chesterfield wrote to Johnson saying that he hoped he would dedicate the dictionary to him. The letter that Johnson wrote back to Lord Chesterfield is very famous. It is very sarcastic (funny in an unkind way). Johnson said to him that it would have been nice to have had help when he was needing it. He said, sarcastically, that a patron was someone who stands on the river bank watching a man drowning and then, when then the drowning man is saved, asks him whether he can help. The letter made Lord Chesterfield look very silly.