you've got to be out of your mind

What you're saying, suggesting, or proposing is outrageous, ridiculous, or crazy! A: "I want to go sky-diving for my 40th birthday!" B: "You've got to be out of your mind! There's no way I'm jumping out of an airplane, even on your birthday!" A: "I was putting in 100-hour weeks to get this project done on time." B: "You've got to be out of your mind if you think that that's an acceptable way to work." A: "All we need to do is destabilize the global economy, and our company would be poised to assume total market dominance!" B: "So you're willing to plunge the world into chaos just to become a bit more profitable? You've got to be out of your mind!"