So, we're getting the "Ship of Theseus" discussion essentially.
Link:
Ship of Theseus
For those of you who don't know, basically, that is a philosophical example of identity. If you take a brand new ship, named the "Ship of Theseus" it's pretty clear what the Ship of Theseus is.
But then it gets old and some parts need to be replaced. At first it is one board, then another. Eventually, all of the boards have been replaced. Is it still the ship of Theseus? Most would say yes.
But what if the old boards were still good? They were just replaced proactively, before they started rotting. And there is a pile of the old boards. And someone comes along and builds and exact replica of the Ship of Thesus out of the old boards. Now there are two identical ships. The first one was the one most people agreed was the Ship of Theseus. The second one is in exactly the same shape as the Ship of Thesus
and built out of all the same exact materials as the original Ship of Theseus.
So the question becomes: are there now two Ships of Theseus? If not, which one is really the actual Ship of Theseus and which one is a false one? Or, if there are now no Ships of Theseus, at what point did that occur? When 1 board got replaced? When half the boards were replaced? When the last board was replaced?
As this relates to D&D:
In my opinion, 4e has had enough "boards" replaced that it is no longer D&D (for me). I absolutely understand how others could have differing opinions and be equally correct.
Conversely, I consider paizo's Pathfinder to be D&D. I also understand how others would be aghast at this statement, decrying it as blasphemy.
However, given the responses to this thread so far, and the idea of the Ship of Theseus, it also appears that the only "pure" D&D is OD&D. After that, there have been a number of "copiers" or "evolvements" including probably all of the examples I gave in my original post.
To some 4e is D&D. To some, OSRIC is. To some Runequest and Warhammer are. To some, none of these are.
I guess my conclusion at this point (and I'm still flexible/undecided...this is just my current working theory) is that, like the ship, it is a matter of degree. The more something is changed, and the more the original is copied the more blurry its identity becomes.
That said, would it be fair to say that 2nd edition D&D is "more" D&D than 3rd and that 3rd is "more" D&D than 4th?
And if so, would it also be fair to say that OSRIC or Castles and Crusades (or another retroclone) is "more" D&D than either 3rd or 4th?