Riemannian manifold

Or things like arithmetic can mentally exist.

Or Riemannian tense or calculus can exist.

Or whatever it may be.

Abstract mathematics can exist.

This was the work of Einstein.

His theory simply is that our space-time system is non-Euclidean and Riemannian, that it is a spherical four-dimensional system, unbounded and finite, imposing on us restrictions and at the same time concealing from us our limitations.

And his originality is that he discovered the means of bringing this new concept to the test of experiment and applied it to the solution of actual scientific problems.

The physics of relativity, therefore, is a complete reversal of the physics of materialism.