philosophy
Theory of ideas
There is a real of Ideas, the deepest reality, which is eternal and unchanging, and provides source of all we can name or speak of. And it builds upon Pythagoras. we come into close contact with the world of eternal, perfect Ideas when we deal in mathematics concepts like numbers, or Platonic solids.
Metaphysics
You cannot disprove this. There is no physical experiment or logical proof that can distinguish between a universe that is billions of years old and one created five days ago