Beating A Dead Horse ( forcing an issue that is already closed ... )

You are beating a dead horse when you insist on talking about something that cannot be changed. Example: "I'd like to talk with you again about what happened." Reply: "Oh, come on. Let's not beat a dead horse."

Beating a dead horse is an action that has no purpose, because no matter how hard or how long you beat a dead horse, it is not going to get up and run. Example: "Let's not talk about it any more. Okay?" Reply: "You're right. We're just beating a dead horse."

To repeatedly bring up a particular topic with no chance of affecting the outcome is beating a dead horse. Example: "Dad, are you sure we can't get a new computer for the upstairs?" Reply: "Son, we talked about this and the decision was 'no'. You are beating a dead horse."

BEAT (OR FLOG) A DEAD HORSE - "Though he supported the measure, British politician and orator John Bright thought the Reform Bill of 1867, which called for more democratic representation, would never be passed by Parliament. Trying to rouse Parliament from its apathy on the issue, he said in a speech, would be like trying to 'flog a dead horse' to make it pull a load. This is the first recorded use of the expression, which is still common for 'trying to revive interest in an apparently hopeless issue.'." From the "Encyclopedia of Word and Phrase Origins" by Robert Hendrickson (Fact on File, New York, 1997)