Another way to look at it is that property setters (or whatever mechanism is used to directly mutate an object’s sub-data) is not meaningfully different from a method doing the same. You could even call it syntax sugar for the same.
Objects refer to other objects using their (immutable) identity. In turn, resolving identities to objects requires (version) scope which can be in the past or present.
Are you storing the version as part of the object? If so, they’re no longer equal values regardless of identity. If not, what purpose is there in versioning the same value? Even if there is a purpose, are same-value-different-version objects not otherwise interchangeable unless/until some value change does occur?
That’s exactly the point I started with!
> Conversely, two objects can have the same 'value' while having different identities. Values and objects are different beasts.
Agree completely. My point—my only point—was that identity implies mutability. Without mutability, identity distinct from value doesn’t mean anything.