Ontic vs epistemic

In plain terms

Here is the problem. Quantum mechanics keeps two kinds of statement in one notation. "The atom is here" sounds like a fact about the world. "The atom has a 30 percent chance of being here" sounds like a fact about what you know. The wavefunction carries both voices at once, and a century of argument has been about which voice is fundamental.

The map-versus-territory distinction is old and boring until you enforce it. Ontic: belonging to the territory, true whether or not anyone looks. Epistemic: belonging to the map some agent or apparatus draws. The trouble starts when a map-fact is mistaken for a territory-fact -- when a change in the description is read as a change in the world.

Collapse is the canonical casualty. If the state is a map, its abrupt update on measurement is no stranger than a weather forecast changing when you open the curtains.

In CSD

CSD makes the split load-bearing and never lets it blur. The outcome regions a measurement context defines live on the projected state space, and they are epistemic: the apparatus fixes the partition, and the partition is a description. The measure that weights those regions is ontic: an invariant volume on the constraint surface itself, fixed by symmetry, indifferent to anyone's knowledge.

The Born rule is precisely the handshake: an epistemic region, weighed by an ontic volume. Measurement is the ontic selection -- the record, on the surface -- of which epistemic region the one real trajectory realises. Keeping the two levels distinct is not philosophical hygiene; it is the structure of the reconstruction.

Mathematically

The two-strata reading is written into the axiom ledger. The operational stratum speaks the effect-and-density language and carries the Gleason-type representation; the ontic stratum computes weights as ratios of the Liouville measure over the preparation region. The corpus proves the two strata meet: the same Born vector is reached by the operational route and by the volume route, through structurally distinct machinery.