"If I can imagine it, it is possible" seems to greatly depend on how you define imagine. I can imagine a little box that gives off energy but requires none to power it (infinite energy, which is not possible) but I can not begin to imagine the inner workings of this box. If you can imagine every aspect of something, then it can exist, you don't have to imagine every aspect, just be able too. I can imagine a car, but u don't know every part of it, but I can imagine how the parts would all work.