Ernst Mach...on absolutes

No one is competant to assert things about absolute space and absolute motion. They are pure matters of thought that cannot be produced in experience. All our principles of mechanics, as we have shown in detail, are experienced knowledge concerning the relative positions and motions of bodies. They could not be, and were not, admitted in the areas in which they are now recognized as valid, without previous testing. No one is warranted in extending these principles beyond the boundaries of experience. In fact, such an extension is meaningless, as no one would possess the knowledge to make use of it.

- Die Mechanik in ihrer Entwicklung, 1912