I suggest (a) that personhood should be be identified with the pattern embodied by the body at any given point in time, and (b) this is due to the fact that there is no continuity of the body through time, only the (dynamic) pattern.
I disagree. Given what you said earlier, I believe you are also still playing Devil's advocate, and are making some really good points, but I don't yet see them as sufficient to outweigh the situation as I've outlined it. Specifically, where
original cells make copies of themselves or
use materials that are ours, a very strong case for continuity can be made.
The alternative boils down to assuming there is never any continuity of anything other than the universe as a whole beginning with the Big Bang. In other words everything we're made of came from the stars, likely the products of some supernova. If at some point we don't claim those raw materials as ours, then we never become persons physically, and if we never become persons physically, there can be no pattern of a person to copy.
We can plainly see from this fact, that there are only two possibilities. At some point the raw materials either must become a person, or there are no persons, only the continuity of Big Bangs > stars > supernovas & planets. Given that we accept that at some point raw materials become persons, then we can trace when and where that happens all the way back to conception. However we cannot do that with a copy.
The physical material of our bodies is constantly being recycled. Furthermore, according to QFT, our most rigorous and accurate model of reality:
And do they fundamentally describe our entire Universe, or do we require something else?
www.forbes.com
This means that at the most fundamental level, there is zero continuity of physical substrate. Our bodies, as complex as they are, are akin to waves moving through a medium (in this case, a non-classical medium, but a medium nonetheless).
A wave has no physical continuity (in the sense we have been discussing); it is a pattern embodied by a liquid medium. To sharpen this analogy, we could imagine a wave moving through a water medium into an oil medium. The wave would continue despite being embodied in a different physical medium.
All the above is taken into account with the preceding explanation.
To your point about our bodies taking in external atoms and absorbing them; I could argue that there is a causal continuity between my body, the copy machine, and the new body. All connected causally, thus continuity maintained. Where we draw the line with such physical/causal continuity is arbitrary.
I don't think "arbitrary" is necessarily fitting. There is a big difference between being causally connected by a common external situation, and being causally connected by an internal situation.
Perhaps here we can use the analogy of a torch relay. In such a race there is continuity of the torch throughout the time and distance of the race by the team that is in custody of the torch. All meaning for the race would disappear if the torch could simply be copied and handed to the team member at the end of the race.
Also, the importance of parentage was completely overlooked. The person who was given birth by the copy machine cannot possibly be the same person the original's mother gave birth to. There is no physical internal continuity or connection whatsoever. There is only a facsimile.
Perhaps however, and maybe you will find this interesting, if the copy machine was complex enough to create an
original person, then we'd have a whole other scenario, especially if the copy machine was networked. Right? I would argue that such a situation would essentially be the creation of a new race altogether, and then I think your argument would be very difficult or even impossible to dispute. Great discussion !