What it is
Consciousness is the felt quality of being someone: seeing red, tasting salt, worrying about tomorrow. It is the one thing each of us knows directly and the hardest thing to explain from the outside.
Philosophers separate the “easy” problems, how a brain discriminates, reports and controls behaviour, from the “hard” problem: why any of that processing is accompanied by experience at all. Scientific theories such as the global workspace and integrated information theories each explain part of the picture; none is accepted as complete.
Four scientific theories of consciousness
The main families of theory, each in one line.
- 01Global workspaceExperience is information broadcast widely across the brain.
- 02Higher-orderA state is conscious when the mind represents itself as being in it.
- 03Integrated informationConsciousness tracks how much a system integrates information.
- 04Predictive processingExperience is the brain’s best prediction of its causes.
Source: Stanford Encyclopedia of Philosophy
A diagram of ideas, not a measurement.
Ideas to carry
- 1
The hard problem
Explaining what the brain does is not obviously the same as explaining why it feels like something.
- 2
A stream, not snapshots
William James described consciousness as a continuous flow rather than a sequence of separate pictures.
- 3
Theories in competition
Workspace, higher-order and integrated-information theories make different predictions, and experiments are now testing them against each other.
Established What we know
- In The Principles of Psychology (1890) William James introduced the image of a “stream of thought”, or stream of consciousness.[1]
- Philosophers distinguish explaining cognitive functions from explaining why they are accompanied by experience, often called the hard problem of consciousness.[2]
- Phenomenology, founded by Edmund Husserl, studies the structures of experience as it is lived, from the first-person point of view.[3]
Interpretation The older lens · Vedanta
The Mandukya Upanishad maps waking, dreaming and deep sleep, and points to a fourth state, turiya, the awareness present in all three.
Reading
- 1890The Principles of PsychologyWilliam James
- 1900–01Logical InvestigationsEdmund Husserl
- 2021Being YouAnil Seth
Scientists: what is consciousness?
Consciousness, reading this: 👀
Connected subjects, projects and writing
- Quantum mechanicsSubject · Cosmos
Interpretation The measurement problem asks what counts as an observation. Some read a role for mind in it; mainstream physics does not require one.
- AI and neural networksSubject · Intelligence
Perspective Whether systems that process information like this could ever have experience is an open question.
- PerceptionSubject · Origin
How a brain turns signals into a world, and why attention and expectation change what we see.
- NondualitySubject · Origin
Traditions that question the line between the one who experiences and what is experienced.
- IdentitySubject · Origin
The memories, habits, roles and languages that make a person, and what keeps them the same over time.
- PhilosophySubject · Origin
The habit of asking what we are actually doing and why: ethics, freedom, obligation and the examined life.
- Questions beneath the surfaceEssay · Origin
Why I read across philosophy, consciousness and religious traditions, and the rules I hold myself to when writing about them.
Sources
- The Principles of Psychology, William James Classics in the History of Psychology (York University), 1890. Checked 5 Nov 2026.
- Consciousness Stanford Encyclopedia of Philosophy. Checked 5 Nov 2026.
- Phenomenology Stanford Encyclopedia of Philosophy. Checked 5 Nov 2026.