R
rossum
Guest
All axioms are made up. None are imaginary, at least not within the particular axiomatic system that uses them.This doesn’t prove to me that all axioms are made-up or imaginary.
For instance in geometry, there are different versions of the parallel axiom: “Given a straight line and a point not on the line there are X lines parallel to the first line and passing through the point.”
X = 0 gives spherical geometry. X = 1 gives Euclidian geometry and X = 2 or more gives hyperbolic (or Lobachevskian) geometry. They are made up because we can pick any of them at will, so long as we remain consistent within the particular axiomatic system. For example, in spherical geometry the angles of a triangle add up to more than 180°, while in hyperbolic geometry they add up to less.
We can make up whatever axioms we want (as long as they are self-consistent). They do not have to conform to the external world.
Mathematicians are happy working in the abstract with any convenient set of axioms. Scientists work with the external world, so they select from the wide range of mathematical axioms available, those axioms which best match the world the scientists study. The good match between scientific mathematics and the world is due to the good selection of axioms to use by scientists. It does not have any deep philosophical significance, just scientists picking the tools that work best from a wide range of different possible tools/axioms.
Scientific mathematics is designed by scientists to match the external world to a high degree of accuracy. Nothing more is needed to explain the observed match.