I will give you an example:
If say, I tell you I have a system inside a black box, and I tell you I can get more energy out from it than I put in on a continuous basis, with no loss of energy to the system over time, you should be able to tell me that is impossible based on the known laws of physics.
You don't need to know how it is designed, or what is going on inside the box.
You could dismiss it out of hand, and no one here would dispute your claim that my design will not work.
Without some major change in the laws of physics it simply will not work.