[onhn]

"The counterfactuals that matter to science and physics, and that have so far been neglected, are facts about what could or could not be made to happen to physical systems; about what is possible or impossible."

On the contrary, if I had to describe theoretical physics in a nutshell, I would say it is entirely about what is impossible. Pick any physical law or theorem. I cannot exceed the speed of light. I cannot globally decrease entropy. I cannot measure a force between two static electric charges in vacuum that deviates from the Coulomb force law.

[HPsquared]

Also basic quantum physics: it's all about the "possible" state of a system (e.g the wave function of an electron).