**Statement:** Distinguishability IS information; therefore information is ontologically primitive.
The 20th-century revolution: physics IS information processing.
Quantum state = information carrier:
|ψ⟩ ∈ H is not a "thing" but a description of what we can predict. The Copenhagen interpretation makes this explicit: the wavefunction is epistemic (knowledge-encoding), not ontic (stuff-encoding).
Measurement = information extraction:
Observable A acting on |ψ⟩ yields eigenvalue a with probability |⟨a|ψ⟩|². This is information transfer from quantum system to observer.
Entanglement = information correlation:
|Ψ⟩ = |↑↓⟩ - |↓↑⟩ encodes correlation without transmitting any physical substance. Bell violations prove this correlation exceeds classical information limits → quantum information is primary.
Entropy as uncertainty measure:
H(X) = -\sum_{x \in \mathcal{X}} p(x) \log_2 p(x)
Properties that make it fundamental: