How to Define Consciousness?

Direct Answer

The honest answer is that consciousness has no single agreed definition, and the attempt to define it is itself part of the philosophical problem. The first step is to recognize that the word "consciousness" covers several distinct concepts. Phenomenal consciousness is the felt character of experience — what it is like to see red or feel pain. Access consciousness is the availability of information for reasoning and action — not the experience itself but its functional role. Self-consciousness is awareness of oneself as a subject. Ned Block's famous distinction between phenomenal and access consciousness (1995) showed that these can come apart: a system could have information available for use without any experience, or have experience without reportable access. A useful definition therefore begins by choosing a target: when you ask "what is consciousness?" you must first decide whether you mean experience, function, or self-awareness — and most disputes dissolve or sharpen once this choice is made explicit.

Historical Context

The definitional problem has a long pedigree. Descartes defined mind by consciousness — thought is whatever is immediately present to awareness — which made consciousness the defining property of mind but left it mysterious how it relates to body. Kant analyzed consciousness in terms of the unity of apperception: a single subject to whom all experience belongs. In the twentieth century, behaviorism tried to define consciousness out of existence by identifying it with dispositions to behave; functionalism redefined mental states by causal roles; and the cognitive revolution introduced operational definitions that allowed empirical study. Wittgenstein's warning is pertinent here: many philosophical problems are generated by the grammar of our language, and asking "what is consciousness?" as if it named a single thing may be one of them. The history suggests that definitions of consciousness are not discovered but chosen — and that the choice reflects a theory of what minds are.

Key Arguments & Debates

The contemporary debate offers competing definitional strategies. Phenomenal definitions, favored by Chalmers and Nagel, define consciousness by the what-it-is-like character of experience; they are phenomenologically accurate but methodologically hard, because experience is private. Functional definitions, favored by Dennett and many cognitive scientists, define consciousness by its causal and informational roles; they are empirically tractable but risk leaving out the felt character that motivated the concept. Cognitive definitions in neuroscience — global workspace, recurrent processing, integrated information — identify consciousness with specific mechanisms; they are operational but theory-laden, and different theories yield different definitions. Eliminativist and illusionist definitions deny that phenomenal consciousness exists as we conceive it; they treat the felt quality as an error of self-description. The practical criterion for choosing among these is fit-for-purpose: what do you need the definition to do? If you are measuring consciousness in patients, you need an operational definition; if you are asking whether AI could suffer, you need a phenomenal one; if you are building a theory, you need one that generates testable predictions.

Contemporary Relevance

The definitional question has become urgent in AI and medicine. In AI, whether chatbots are "conscious" depends entirely on definition: by functional criteria, some systems show glimmers; by phenomenal criteria, we cannot even measure the target. The AI welfare debate inherits the ambiguity: the question "could AI suffer?" presupposes a definition of the capacity that matters morally. In medicine, the diagnosis of disorders of consciousness — vegetative states, minimally conscious states — depends on operational definitions, and the choice of definition determines who is treated as a patient with experience. In the law, definitions of consciousness would determine the rights of artificial persons. The lesson is that definitions are not neutral: they encode assumptions, and they have consequences. Defining consciousness well is therefore not a scholastic exercise but a precondition for doing science, ethics, and policy in a world that increasingly contains minds of unknown kinds.

Related Concepts

• What Is Consciousness? — the concept under definition
• What Is Qualia? — the phenomenal content definitions target
• What Is Functionalism? — the functional definitional strategy
• What Is the Explanatory Gap? — the gap definitions try to bridge
• What Is Illusionism? — the definitional strategy of denial
• What Is the Hard Problem of Consciousness? — the problem any definition must face

Further Learning

• Stanford Encyclopedia of Philosophy: Consciousness — the survey of definitions
• Internet Encyclopedia of Philosophy: Consciousness — accessible introduction
• Stanford Encyclopedia of Philosophy: Functionalism — the functional definitional strategy
• Stanford Encyclopedia of Philosophy: Qualia — the phenomenal target of definitions