A philosophical zombie is supposed to be a creature that is functionally/physically identical to you but which lacks qualitative consciousness. Although there is something that it is like for you to drink orange juice just after brushing your teeth, there is nothing that it is like for your zombie twin to do the same thing. Of course there is a huge debate over whether these things are really possible or not and if so what they show about consciousness. I don’t really want to get into this traditional problem (my own view is that the answers are ‘no’ and ‘nothing’), but rather want to discuss some kinds of higher-order zombies.
Disregarding the ‘functionally/physically identical’ bit, a zombie on the higher-order theory of consciousness is a creature that has all of my first-order states but none of my higher-order states. There will be nothing that it is like for this creature to have any of its mental states, even though he and I will be pretty much behaviorally indistinguishable (since conscious mental states have very little function on the higher-order theory (but not ‘no function’, as I argued in The Function of Consciousness in Higher-Order Theories)).
I was recently reading Rosenthal’s Metacognition and Higher-Order Thoughts, which is a response to several commentaries on his 2000 Consciousness & Cognition piece. In it Rosenthal addresses the possibility of a HOT zombie, which is a creature “whose inner life is subjectively indistinguishable from ours despite the lack of sensory states.” A HOT zombie is a creature who has all of my higher-order states but none of my first-order states. This is, of course, a radical version of the objection from the ’empty HOT’ and while it is wildly implausible, it is a theoretical possibility and so something must be said about it.
Now some may find the possibility of a HOT zombie to be paradoxical (in fact one of the commentors does). Rosenthal’s response to this is his usual one. He says,
[T]he intuitive paradox rests on an ambiguity in ‘sensory state.’ The sensory states the HOT zombie would lack are only nonconscious states. Since conscious states are states one is conscious of oneself as being in, notional states are allthat matter for the purposes of consciousness.
So me and my HOT zombie twin will have indistinguishable conscious experience but, as Rosenthal notes, we will behave in very different ways. This is because the first-order states that the HOT zombie lacks are the states that have most of the causal efficacy.
Now this is all very interesting in its own right (but I don’t want to discuss it now…Pete and I have argued over this stuff beofre, like here), but last night, as I was introspecting while listening to some live jazz music, I started thinking about another kind of higher-order zombie; an introspective HOT zombie. Introspection, on the higher-order theory, is the occurance of a suitable higher-order state that is about one’s higher-order states. A conscious experience occurs when one is conscious of oneself as being in a certain first-order state and in introspection one becomes conscious of oneself as being conscious of a certain higher-order state. Since introspection is simply the occurance of some third-order state about my second-order states all of the issues about misrepresentation come up again at this higher level.
So we could (theoretically) have a creature who lacked all of my first-order states and all of my second-order states but which had all of my third-order states. This is the introspective HOT zombie. This creature has no conscious states even though it seems to him as though he does. When I see red I will be conscious of the red and conscious of myself as seeing red and were I to introspect I would be conscious of myself as being conscious of myself as seeing red, but the introspective HOT zombie is just conscious of itself as being conscious of itself as seeing red. What will it be like for this ceature? It will be like consciously and introspectively seeing red.
As if this wasn’t bizzare enough we could (again theoretically) have a case of a creature who had a first-order state that was a seeing of red and that had a HOT misrepresenting this first-order state as a seeing of green. What it is like for this creature to have the first-order state will be like seeing green so it will be like seeing green for this creature. Now suppose that this creature introspects its conscious mental states and (for some reason) has a third-order state that represents the second-order state as a seeing of red (that is it accidently gets things right). What will it be like for this creature? Are we to say that this creature is conscious of itself as seeing red and not conscious of itself as seeing red? That what it is like for this creature is like seeing red and not seeing red?
I will have to think about this some more…