pyhsical laws are invariances across observers

facts are observer-relative, but the invariances across observers are what we call physical laws:

Under relational metaphysics, the intrinsic vs observer-relative distinction dissolves

Every property is observer-relative in some sense (which mapping fixes a computation, which metaphors we use, …).
→ Replace the binary with a spectrum, parameterised by the (size of the) invariance group:

At one end, we have what we believe to be observer-invariant … according to current physics (speed of light, rest mass, electric charge, CPT symmetry).
But today’s wide invariance group might be tomorrow’s narrow one, as science asymptotically approximates objective reality (intrinsic scalar mass→rest-mass+frame-dependent energy/momentum; euclidian spacetime geometry→GR; QM…).

In the middle, “observer-variable” things that exist for any observer but vary with the observer (velocity, simultaneity, energy, basis of measurement for spin).

At the other end, observer-specific things – only exists relative to a particular observer.
Money (not intrinsically money absent the institution; ontologically observer-relative, but epistemically objective – we can still make objective claims about money), a screwdriver, positive vs negative current, …

→ There is no thing-in-itself.

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