Consciousness provides us with a way of interpreting the world and our interactions with it. For example, I am conscious of there being a computer in front of me through the use of my sense of sight and my sense of touch etc. What is actually occurring is that I am conscious of experiential properties. But consciousness is not merely consciousness of, or transitive consciousness, it may also be intransitive, or the merit of a state being a conscious state. The aim of Block's 'Concepts of Consciousness' is to disambiguate the concept of consciousness. Block's method is to differentiate between two different but related aspects of consciousness that are often confused; phenomenal-consciousness, or P-consciousness, and access-consciousness, or A-consciousness. In what follows I will outline Block's concepts of both P-consciousness and A-consciousness and their relationship to our understanding of consciousness. I will also suggest that Block's concept of A-consciousness is too weak to be given the status of a conscious state.
At the beginning of 'Concepts of Consciousness' Block (p. 206) claims that P-consciousness can not be defined in 'any remy non-circular way'. This need not be of concern however; we can honestly discuss P-consciousnessness by informing it's existence and discussing examples that are both actually and conceptually possible. For all P-conscious states there is something that it is like to be in that given state; P-conscious states are those states that have an experiential property (Block 2002, p. 206). A P-conscious state may be my experience of the computer in front of me, as stated before, or my experience of a certain mental state such as an emotion. P-consciousness is, therefore, representational of a given property.
P-conscious places information into what I'll call the global workspace of consciousness or GWC. When I have a particular experience my P-consciousness processes the data in that experience and stores it in the GWC1 for me to access. For the purposes of explanation I'll assume that this data is stored in tables, however this is actually the case is not relevant. This is where Block's concept of A-consciousness becomes apparent. The purpose of A-consciousness is to access the data that the P-consciousness process has stored in the tables of the GWC and broadcast this data for open use in the process of reasoning. We can describe this in Block's (2002, p. 208) terms by stating that A-consciousness is 'an information processing correlate of P-consciousness'.
Block (2002, p. 209) believes that P-consciousness and A-consciousness interact but this need not necessarily be the case. If we take the above definitions to be the case then P-consciousness' temporal location precedes the temporal location of A-consciousness. For P-consciousness to occur A-consciousness need not be the case so there is no reason to suppose that P-consciousness and A-consciousness must interact. But is this what Block is claiming by saying that it insists that P-consciousness and A-consciousness interact, that they necessarily must interact. Or is he claiming that if P-consciousness and A-consciousness are the case then they may interact? While Block makes no explicit statement regarding this issue it is evident that the latter is the case. If both P-consciousness and A-consciousness are the case, that is they are both temporary appearance, then they interact. If one of either P-consciousness or A-consciousness is not the case, a situation that Block supports2, then of course there is no scope for interaction between the two.
According to the above definitions of P-consciousness and A-consciousness it is entirely possible for P-consciousness to exist without A-consciousness solely on the basis that it can occur temporally earlier; for P-consciousness to hold A-consciousness need not be the case. But for what duration may a P-conscious state exist without there being a correlation A-conscious state and is there a 'real-world' example of such a state? In answer to the first question the duration of the state of P-consciousness existing independent of a correlate A-conscious state is of little concern, the ability for P-consciousness to exist without A-consciousness for any duration is enough for it to hold as an entirely independent state. As for a 'real-world' example, today I decided to work in my dining room near my kitchen. During the course of the day I was absorbed in the writing of this essay and developed a headache so I stopped working and subsequently became aware
that my refrigerator was malfunctioning and producing a high pitched noise. This noise had contributed to me developing a headache. Before I developed the headache I was, or at least could have been, P-conscious of the high pitched noise but only upon developing a headache was this P-conscious state broadcast, or A-conscious.
Whether A-consciousness can exist without P-consciousness is much more problematic. By the definition given earlier, one in line with Block's position, A-consciousness is dependent upon P-consciousness. Block does claim, however, that A-consciousness can exist independently of P-consciousness. Block uses the example of a blindsight patient, a limited partial zombie (Block 2002, p. 211). Blindsighters are people, sometimes animals too, who have had a section of their visual field damaged to such an extent that they are now blind in that area. When asked to identify a property in their blind field they are specifically accurate at 'guessing' the details of the given property (Carruthers 2001). This example is particularly troublesome. Block admits that when the blindsighter (or superblindsighter in this case, someone who does not need to be provoked to guess what may be in their blind field) has a thought that there is a property in their blind field this thought would be both A- conscious and P-conscious. However, Block does not concern himself with the thought but with the state that wave rise to the thought. Block claims that this state is A-conscious only, it is not P-conscious at all (Block 2002, p. 211).
The problem with this position is that for a state to be A-conscious it needs to be A-conscious of something. In the definition given earlier A-consciousness occurs by accessing and broadcasting the contents of a table in the GWC. Block (2002, p. 212) claims that the blindsighter 'just knows' the content of his / her blind field without reference to the GWC or any P-conscious data. If this is the case then what the blindsighter is displaying is not A-consciousness but something else entirely, the blindsighter is not accessing any content to be broadcast. Perhaps the blindsighter is conceptually closed to the P-conscious experience of the property in their visual field and the subsequent A-conscious process simply appears to exist independently of P-consciousness. Whatever the case, Block leaves his position ambiguous at best.
Let us suppose for a moment that A-consciousness is conceptually possible. If A-consciousness is a distinct form of consciousness, a form that is not dependent upon P-consciousness, then what is the role of P-consciousness? Chalmers (1997, p. 421) claims that A-consciousness is conceptually possible and that A-consciousness does all of the conscious work; but if A-consciousness is all that is needed for a being to be functionally conscious then it would be possible for there to exist humans who possess no P-conscious states, call them zombies, but who are functionally equivalent to humans (Silby 1998) . But zombies are not actually the case and neither does A-consciousness occur independently of P-consciousness (Rosenthal 1997, p. 156). A-consciousness is best explained as an aspect of P-consciousness, it is dependent upon P-consciousness for its existence. By claiming that A-consciousness is an independent form of consciousness Block is over extending its argument. Block (2002, p. 210) even makes note that 'A-consciousness can be a kind of consciousness even if it is parasitic on … P-consciousness'. A-consciousness is not consciousness this is too strong a claim; it is a process of P-consciousness that exists only in relation to previous P-conscious states and, importantly, P-consciousness' interaction with the GWC.
Block's distinction between P-consciousness and A-consciousness, if that's what we will now call it, is suddenless important. By outlining the parameters of the A-state Block we provide with a better picture of a 'complete' consciousness, one in which we know how A-states of consciousness function, particularly in relation to P-conscious states. But if we accept Block's position on A-consciousness we encounter numerous problems such as the functionally equivalent zombie. Perhaps to get the most 'complete' concept of consciousness Block's liberal position on A-states needs to be avoided, this way P-conscious states and their eventual existence A-states can be understood as they actually exist, in relation to one another.
1. It is important to note that the GWC is global only in the sense that is global for the individual, the whole of an individual can access the GWC.
2. See Block 2002, pp. 211-213.
Block, N 2002, 'Concepts of Consciousness' in Chalmers, D (ed.), Philosophy of Mind: Classical and Contemporary Readings, Oxford University Press, Melbourne.
Carruthers, P 2001, 'Higher-Order Theories of Consciousness', in Zalta, E (ed.), The Stanford Encyclopedia of Philosophy (Summer 2001 Edition), View 1 May 2007,.
Chalmers, D 1997, 'Availability: The Cognitive Basis of Experience, in Block, N Flanagan, O & Guzelere, G (eds), The Nature of Consciousness, MIT Press, pp. 421-425.
Rosenthal, D 1997, 'Phenomenal Consciousness and What its Like', in Behavioral and Brain Sciences, Vol. 20, No. 1, pp. 156-157.
Silby, B 1998, On a Distinction Between Access and Phenomenal Consciousness, Viewed 2 May 2007,.