Access vs phenomenal consciousness
Explanation
Ned Block, in a very influential 1995 article, proposed distinguishing two different concepts of consciousness that are often confused in debates: access consciousness (A-consciousness) and phenomenal consciousness (P-consciousness). The first is functional: a content is A-conscious when it is available to control reasoning, verbal report and rational behaviour. The second is experiential: a content is P-conscious when there is something it is like to have it.
The importance of the distinction is that the two could come apart. A content could be A-conscious without being P-conscious (rationally manipulable but empty of experience, as in a functional zombie) or P-conscious without being A-conscious (experienced but not accessible for report, as perhaps in peripheral vision or in the fovea during perceptual overload).
Evidence for the distinction comes from phenomenal overflow: when we look at a scene, we subjectively feel that we have rich experience of many details, but we can only report a fraction. Experiments such as Sperling's partial-report paradigm suggest that there is perceptual information phenomenally present that is not fully accessible to cognitive control systems.
The distinction illuminates debates between theories. Theories such as GNW (Global Neuronal Workspace) would be fundamentally theories of A-consciousness: they explain how information is made available to cognitive systems. Theories such as IIT (Integrated Information Theory) aspire to explain P-consciousness: which physical patterns are phenomenally experiential.
The debate becomes complicated when one asks whether the two consciousnesses are really independent or whether they are necessarily connected. Dennett denies the distinction: what we call P-consciousness is just A-consciousness described phenomenologically. Chalmers accepts it and considers it key to formulating the hard problem. Tye, Burge and others occupy intermediate positions.
Block's distinction has structured much of the contemporary debate. It allows precise formulation of the explanandum: do we want to explain why certain contents are cognitively accessible, or why there is subjective experience? The answer defines what theory we are looking for and what would count as success. Few philosophical distinctions have had so much impact on the neuroscience of consciousness.
Strengths
- An analytically clear and empirically operationalisable distinction.
- Productively structures the field.
- Supports hard-problem intuitions.
- Inspires specific experimental research.
Main critiques
- Critics maintain that the separation is fictitious or exaggerated.
- 'Phenomenal overflow' is empirically disputed.
- Risk of duplicating entities unnecessarily.
- Some: phenomenal consciousness is illusion, there is only access.