BOP should always be shared in debates

I agree that the Burden of Proof (BoP) should often be shared between the opposing sides in a debate, however the BoP must sometimes fall on only side. This is what I will argue for. Pro has not stated otherwise, so I will present my argument in this round. Note that according to the resolution, highlighting "always", I only have to give one or a few examples of debates where the BoP should not be shared. The burden of proof - scientific and non-scientific"An extraordinary claim requires extraordinary proof. " - Marcello Truzzi [1] Imagine a claim, of something thought impossible. Let's say I have a cube in my living room. The cube: Is floating Has no matter or antimatter (and thus no gravity) Is invisible Emits or reflects no lightwaves Emits or reflects no soundwaves Any mass can move trough it without restrictions Etc (it has no characteristics that can be detected by us) There is clearly no way to prove or disprove the existence of this cube, by our ways of detection. Yet I still claim this cube to be there. I am making an extraordinary claim here, and as Marcello Truzzi would agree, I should need extraordinary proof to back it up. I am the one making this claim, and I should provide the proof. Why should the opposing side of the claim need to provide proof, when there is simply no way to disprove the statement that this cube exists? The scientific philosopher Karl Popper defines a theory as scientific or non-scientific (pseudoscience or imagination) by its falsifiability [2]. Falsifiable means that it is possible to falsify. This obviously does not mean that every scientific theory needs to be wrong, only that it must, in theory, be possible to falsify it to know whether it is wrong or not. We derive from this that my previous example of a floating cube is not a scientific theory. To bring this back down on the ground, we can look at another example, and perhaps a more standard topic on this site: "The US is more powerful than China". Here, the BoP should quite obviously be shared, because the theory can be falsified - the one side can prove that the US is more powerful, and vice versa. To conclude: If the theory is falsifiable, the BoP can be shared. However, if the theory is not falsifiable, the BoP must be on the one side making the claim. This is in order to force the side making the claim to present proof, which can then be disproved (falsifying the theory) or verified (making the theory valid unless it conflicts with other theories that are better supported). In other cases:While this was the most essential type of debates where the Burden of Proof actually must be shared, the Burden of Proof is often forced on one side by the Instigator in a debate. This usually happens when a claim simply conflicts with what is regarded as "common sense", or when the claim conflicts with things that are already physically established. In these cases I more often than not believe that the BoP should be shared, for a more equal, open and interesting debate. However, there is still a minority of debates where Sources[1] Wikipedia, "Marcello Truzzi", . http://goo.gl..., (accessed 23. 05. 2015). [2] Shuttleworth, Martyn. "Falsifiability". Explorable. com. . https://goo.gl...;(accessed 23. 05. 2015)