Depth of anaesthesia: a number on a monitor standing in for something nobody can observe.
Consciousness
The fact that there is something it is like to be a subject - awareness itself, rather than what one is aware of.
- Theme
- Mind, self and consciousness
- Tradition
- Cross-tradition
- Term fixed
- 1641
In plain terms
Some things are like something to be. There is a way it is to be you now, reading this, and there is presumably no way at all that it is to be the chair.
That is the whole subject, and it is remarkably hard to say anything further without either changing the topic or sounding mystical. Explaining how a brain discriminates light, stores information and reports on itself is difficult but tractable. Explaining why any of that is accompanied by experience is a different order of question, because the explanation would have to say why there is not simply darkness inside while all the processing goes on.
And the evidence is peculiar. Each of us has exactly one case, known with total certainty and inaccessible to everyone else.
As a philosopher would put it
Block's distinction is standard: access consciousness is information being available for reasoning, report and control; phenomenal consciousness is there being something it is like. Access is what experiments can address. Phenomenal consciousness is what Chalmers calls the hard problem, and the two come apart in principle.
The main theories divide sharply. Global workspace theory makes consciousness a matter of information being broadcast widely across the brain. Integrated information theory identifies it with a measure of integration, which has the consequence that simple systems have a small amount of it. Higher-order theories make a state conscious by being represented by another state. Illusionism denies there is phenomenal consciousness to explain and treats the appearance as itself the thing requiring explanation.
Outside the Western frame the questions are posed differently. Advaita takes consciousness to be self-luminous and not a property of anything, which makes it the wrong sort of thing to be explained by a brain; Yogācāra analyses it into eight functional consciousnesses with no unifying subject.
Where you meet it
Anaesthetists have to know whether a patient is conscious, and they have no direct way to find out. Depth-of-anaesthesia monitors process the EEG into a single number, usually scaled so that around forty to sixty indicates adequate anaesthesia. The number is a statistical correlate, and everyone using it knows that.
The United Kingdom's NAP5 study, published in 2014, examined accidental awareness during general anaesthesia across every public hospital in Britain and Ireland. Reported incidence was about one in nineteen thousand, and considerably higher for particular techniques. Some patients reported paralysis without pain; some reported distress that persisted for years.
What the study documents is a gap that no instrument closed. The monitor reads a proxy, the paralysis removes the behavioural signs, and the only source of evidence is a report afterwards from the one person who was there. Consciousness turned out to be a variable that a whole speciality must control without being able to observe.
What is actually disputed
Whether there is a hard problem.
One camp holds that explaining all the functions - discrimination, integration, report, control - leaves the central fact untouched, and that no functional story could entail that there is something it is like. The other holds that this intuition is exactly what needs explaining, not what needs accommodating: once every function is accounted for, the sense that something remains is itself a cognitive effect, and treating it as data about the world is the error.
The stakes are not academic. If consciousness is a matter of function it can in principle be built and measured. If it is not, then no test could settle whether an animal, a patient with severe brain injury or a machine has it, and every practical decision in that area rests on a judgement nothing could confirm.
Commonly confused with
- Qualia 1929 Qualia are what particular experiences are like. Consciousness is that there is experience at all. A theory can grant one and deny the other.
Defined against
- The unconscious The pair marks the boundary of the subject, and the discovery that most mental work happens on the far side of it
Philosophers
- René Descartes Consciousness as the one thing that cannot be doubted
- John Locke Consciousness as what makes experience one person's
- Edmund Husserl The structure of experience described from inside
- Maurice Jean Jacques Merleau-Ponty Consciousness as bodily and situated rather than a spectator
- Shankara Consciousness as self-luminous, and not a property of anything
Works
- Meditations on First Philosophy The certainty of one's own awareness
- The Conscious Mind The hard problem stated at length
- Consciousness Explained The case that the hard problem dissolves
- Phenomenology of Perception Consciousness as embodied
- Brahmasutra Bhasya Consciousness as the ground rather than a product
Schools
- Cartesianism Where consciousness becomes the starting point
- Phenomenology Where its structure is described rather than explained
- Advaita Vedanta Where it is the ground of everything else
- Yogacara Buddhism Where it is analysed into eight functions with no unifying subject
- Vienna Circle Where first-person reports were held to be scientifically empty
Related concepts
Qualia 1929 · Mind c. 450 BC · Self 1694 · Other minds 1865 · The unconscious 1900
The modern sense is Descartes's and Locke's, in the seventeenth century; earlier philosophy discusses awareness at length without treating it as a single problem needing a single name.