But can anyone answer that question? And does that, therefore, mean that everyone's definition of D&D is functionally meaningless? Maybe so. But I would take it one step further: because no one has come up with an adequate definition of what D&D is, we cannot really say that 4E is not D&D because of the continuity of themes, tropes, and rules that it does share with the D&D lineage. In other words, it has enough D&Disms that the owner of the trademark felt they could brand it with the name "D&D," and those who enjoy playing it--and many besides--call it D&D. When it comes down to it, it is only a relatively small percentage of D&D players that would actually claim that it is "not real D&D," even among those that don't like it.
It has enough D&Disms...
in your subjective opinion.
To put it another way, the onus is on those declaring that 4E is not "real D&D" to support their claim in order for it to hold water beyond their own subjective inclinations
I disagree, since I see this as an entirely subjective matter. If it isn't D&D for one and it is for another, both viewpoints are valid for their holders.
The only time an onus if proof arises at all is when one tries to convince the other of the validity of his viewpoint.
Yes, it is a matter of perception. But I think your post only further supports the notion that 4E is D&D in a sense beyond any individual's viewpoint, that is as an inter-subjective agreement. You are still you, even though the parts that make up you are different than what they were 10 years ago; why? Because you are more than the sum of your parts, you are more than just any iteration of who you have been at any given time in your life. You are no less you as a 40-year old as you were you as a 4-year old. You are the entire process, the enter being-in-becoming.
I am only the same me only so long we all agree that sentience is the defining characteristic of human identity, not my physical composition.
D&D doesn't have that luxury, and even if it did, there is no agreement on what the universal essential defining characteristics of the game are. If there were, this thread would not exist.
The Theseus's ship analogy doesn't quite work because you use the phrase "the one he started on." As soon as any changes are made, it isn't "the one he started on." By that definition, only OD&D is real D&D, and everything after--including the supplements--isn't "the one he started with." Therefore the definition and analogy is false.
The classic
SoT analogy is valid- they are both things, not conscious beings. Depending on now you examine them, you can reach either conclusion.
As long as the changes are close replacements, for Theseus and his men (even the ones who joined mid-journey), it is the same ship by any standard they care about- its smells, sounds & textures; its dimensions; the way it handles and parts function; it's graceful lines. It's builders would recognize it...as would anyone who is a shareholder in ownership.
OTOH, at some point it is more new than old, thus in some way a different ship. Not that the crew will notice or care.
However, I'd the changes improve or worsen the ships handling or appearance, Theseus and crew (again, even those who joined mid-voyage) will note the change, and may even lament that the ship is not the same...though they may not agree upon what particular change did it for them.
And despite this, Theseus' creditors will insist that it's the same ship he left on and where's their payment, thank you very much.
The same is true of D&D: by some standards, 4Ed is still D&D, by others, it's not even close.