> Circles and the relationship between their circumference and diameter existed before minds existed There really aren't any circles in the physical universe.

> Circles and the relationship between their circumference and diameter existed before minds existed There really aren't any circles in the physical universe. There aren't any ellipses either. I'm not sure about lines. You're going to hit Planck's constant and the speed of light in any example you name. Charge seems quantized, so you can probably have the integers and fractions, but real numbers are right out.