I find it interesting that we can think about [simple and complex] mathematical structures. How did we get the ability to do so and why we can do so?
I distinguish between mathematical structures and "reality". From my perspective, mathematical structures are being used provide succinct description of the perceptible portion of "reality", the Universe as we say. Need all mathematical structures exist?
What can we say about [biological, AI, or even theoretical] systems that can deal with abstract mathematical structures: to be able to construct, modify, specialise or generalise such structures in a extra-computable manner?