"Sure, a house is real, but what does it look like? That depends on whether you view it from the front or the back. Sure, an electron is real, but is it a wave or a particle? That depends on what sort of experiment you design to detect it. Sure, your theory of the universe works pretty well. But it's not the only theory that works well, and another one, in some cases might work better, even though at other times it works worse. The opposite of a great truth is another great truth."