Hi Geoffrey -

I will let Bob speak for himself in case he has any thoughts on this, but speaking for what went into the report, it's true that we did not take much of an evolutionary psychology perspective, certainly not directly. I actually think it's a live possibility that consciousness is a spandrel--see here and here--although nothing in the report hinged on this. (Note that consciousness having little to no utility is consistent with consciousness being causally efficacious in the production of behavior etc. So no epiphenomenalism here.)

With that said, one consideration that did come up related to your question is the idea that an organism has at most one independent cognitive system. (These are different from cognitive subsystems, of which an organism can have many.) The prevailing idea, as noted in this paper by Carls-Diamante--is that having more than one would be counter-productive in various ways due to, e.g., failures of complete information transfer across the systems. So perhaps this could be connected to your point: having more than one independent system per organism is maladaptive. But of course, Carls-Diamante goes on to suggest that the octopus may be an exception to what is otherwise a rule. As we argue though, even granting this, we are still away far from the core issue, which is whether the octopus houses more than one welfare subject. 

Hi again. Regarding this comment: 

“If it is the case that a "new" welfare subject can be "created" by a traumatic brain injury, then it might well be the case that new welfare subjects are created as one's life progresses. This implies that, as we age, welfare subjects effectively die and new ones are reborn.”

I am not sure this follows. Even if we granted that traumatic brain injury could result in a new welfare subject—which would depend on (i) what welfare subjects are, and (ii) what happens in in brain injury—whether the same thing would happen during the aging process would depend on whether whatever relevant thing happens in the brain injury happens in aging. (For my part, I do not see why this would be the case. Maybe you are thinking of natural neurological changes that happens as we get older?)   

And let me add this. The most neutral way of understanding welfare subjects, to my mind, is just what we say in the report: an individual S be a welfare subject if and only if things can be non-instrumentally good or bad for S. Assuming that our theory of welfare subjects is subordinate to our theory of well-being or welfare, then a welfare subject will just be the kind of thing that can accrue welfare goods and bads—whatever those are. 

Suppose now that x has a traumatic brain injury at t1.  We can then ask:

1. Is there still a welfare subject at t2?
2. Is y at t2 (post trauma) the same welfare subject as x at t1?

The answer to (1) depends on whether whatever is there at t2 can accrue welfare goods and bads. And that depends on what those goods and bads are. If, for example, we adopted a desire-satisfaction view, and the brain injury knocked out the ability to have desires, then tjere would no longer be a welfare subject at t2.

The answer to (2) depends not just on whether there is still a welfare subject at t2 [so a ‘yes’ answer to (1)], but also the kind of thing x fundamentally is—maybe a forensic person, maybe something else--which will determine its persistence conditions, and thus whether it can survive brain injury. (Compare: I am a resident of Texas, but this does have anything to do with what I am fundamentally, as I can survive if I move somewhere else. If I am a forensic person but only in the way I am a Texan, then I can survive not being a forensic person. And if being a welfare subject has nothing to do with being a forensic person, then I can survive as a welfare subject without surviving as a forensic person.) I would assume that if x at t1 = y at t2, then we have the very same welfare subject too, so long as being a welfare subject comes automatically with whatever it takes for us to persist over time.  

Hi Jasper - Thanks for these interesting questions. So speaking for myself, I did not take up the temporality issue--at least not in the way you seem to be suggestion without these cases. I can say something about your brain injury question though. The term 'person' is used in different ways. Sometimes it is used to just mean whatever we are fundamentally. So, if a traumatic brain injury resulted in a numerically distinct person in this sense, then it would be the same thing as death and then ‘birth’ of a new person. In that case, if there was a welfare subject pre-trauma, then there will be a new welfare subject post-trauma, so long as whatever capacities necessary and sufficient for being a welfare subject are preserved. 

On another usage, being a “new person” is just metaphorical, as in what I might say to my daughter if she came home from college super interested in Goth stuff. (My daughter is not quite 5 yet, but who knows…)

Finally, some use ‘person’ in a Lockean (after John Locke) forensic sense, where forensic persons are the kinds of things which can be held morally responsible for their actions, for which prudential concern is rational, etc. There are all sorts of tricky issues here, but one possibility is that *you* can survive even if you do not survive as the same forensic person. Perhaps something like that can happen in certain cases of brain trauma. For example, maybe whatever survives post-trauma is not morally responsible for any pre-trauma actions—precisely because there are none of the same memories, personality, beliefs, and behavioral dispositions. I’d have to think more on how this connection to questions about being/counting welfare subjects, though.

I think which of these different sense of ‘person’ is apt for saying someone is a ‘new person’ post trauma depends a whole lot on the actual details of the trauma in question. 

Hi Ben - Thanks for this. I agree that the PVS case is tricky, and probably not the best example. I assume that you are claiming that PVS patients are still phenomenally conscious, and that you are pointing to this study. (Note though that the authors never use "phenomenally conscious".) However, as expected, the Owen et al study is controversial. I find  this paper helpful when it comes to understanding some of the underlying methodological issues. One issue is whether these patients actually have intentional agency--perhaps suggested by their task responses--as this is often used as the diagnostic criterion for inferring that these subjects are (minimally?) conscious. It's unclear whether they have such agency (see here), although this would not itself eliminate consciousness. So, fair point!