> Bob at time t is still Bob at t+1 even if his state (like position) has changed.
Again, I don't think this is at all evident.
What if we remove a limb? Give him a dose of LSD? Give him a brain tumor? Replace most of his cells as happens to each of us every few years? What change is large enough that it's easier to represent with:
bob = getNext(bob);
...rather than:
bob.foo = bar;
? Is it even harder to represent change one way rather than the other?
Indeed, socially, the concept of identity is a leaky enough abstraction to cause problems; for example if we are criticized for actions that we took years ago, it's easy to get defensive even if we are a different enough person now that we would never take that action now.
Bringing this back to inheritance: if it would make sense to model Bob as an instance of Child one day and as an instance of Octogenarian another day, why not create a new instance of Bob?
You want to argue this from the standpoint of "this is how things are" but I think that there are multiple ways to model Bob and which is appropriate actually depends more on the needs of the system than the true nature of Bob.
Bob’s state might change, but he is still Bob. That would also go for the Ship of Theseus. However you represent it, change is still change, it is still mutability.
We can argue if identity is useful in real life, but most people cling to names and identity, it isn't a controversial subject.
Dynamic inheritance is extremely useful in a programming language, though only a few have it. It is a very OO concept, as are the languages that have explored the concept (e.g. Self, Cecil, among others, even Javascript has this aspect, though not focused enough to use very well).
Again, I don't think this is at all evident.
What if we remove a limb? Give him a dose of LSD? Give him a brain tumor? Replace most of his cells as happens to each of us every few years? What change is large enough that it's easier to represent with:
...rather than: ? Is it even harder to represent change one way rather than the other?Indeed, socially, the concept of identity is a leaky enough abstraction to cause problems; for example if we are criticized for actions that we took years ago, it's easy to get defensive even if we are a different enough person now that we would never take that action now.
Bringing this back to inheritance: if it would make sense to model Bob as an instance of Child one day and as an instance of Octogenarian another day, why not create a new instance of Bob?
You want to argue this from the standpoint of "this is how things are" but I think that there are multiple ways to model Bob and which is appropriate actually depends more on the needs of the system than the true nature of Bob.