The enigma of consciousness

The argument rests on a principle: what I clearly and distinctly conceive as able to exist apart really exists apart, since God could create it so. Now I can conceive my mind, pure thinking thing (res cogitans), with nothing corporeal attributed to it, and body, pure extension (res extensa), with no thought. My essence is therefore to think, and the mind is really distinct from the body, a substance of another nature than the brain. This substance dualism breaks with the Aristotelian soul, form of a body, and at one stroke frees matter for a purely mechanistic physics; yet it bequeaths the problem, which Descartes will struggle to solve, of their union and interaction.

Meditations on First Philosophy, VI

What thinks cannot be of the same nature as what is thought from without: the soul knows the immaterial Forms, it moves itself and outlasts the body's states, traits no arrangement of matter could produce. Consciousness thus belongs to an order other than the sensible, prior to and independent of it, not to a bodily configuration that would generate it. Platonism thereby refuses in advance any reduction of mind to matter, where the Stoics will make the soul a corporeal breath.

Plato, Phaedo; Phaedrus

Chalmers separates the easy problems of consciousness, which concern mechanisms and which science will solve, from the hard problem: why are those mechanisms accompanied by any experience at all? No functional explanation answers it, for describing what a system does leaves untouched what it is like to be one. He concludes that qualia are not reducible to physical processes but are tied to them by laws of nature, and calls his position a naturalistic dualism: consciousness is a fundamental feature of the world, like mass or charge, not a separate substance. He also explores, without adopting it, another route to the same intuition: lodging experience in the intrinsic nature of the physical, of which physics describes only the structure. That option, close to Russellian monism and to panpsychism, remains for him a serious avenue, not the thesis he defends.

"Facing Up to the Problem of Consciousness" (1995) · The Conscious Mind (1996) · "Panpsychism and Panprotopsychism" (2015)

Strawson starts from a certainty he judges firmer than any theory: experience exists, it is what we are most sure of. He then refuses brute emergence: that matter utterly devoid of inwardness should produce lived experience by sheer complexification strikes him as not mysterious, but unintelligible. If one also holds that everything is physical, only one way out remains: the physical already contains, at its fundamental level, something experiential. He therefore presents his panpsychism as a real physicalism, not as adding mind to otherwise inert matter.

"Realistic Monism — Why Physicalism Entails Panpsychism" (2006)

Russell refuses both inherited camps: neither matter nor mind is fundamental, both are built out of one and the same neutral stuff, made of events that can be grouped by the laws of physics or by those of psychology. To this he adds a remark that has since prospered: physics gives us only the structure of things, never their intrinsic nature, and the one portion of the world we know otherwise than by its structure is our own experience, which is precisely what goes on in a brain. The family of positions that lodge experience in that vacant place has since been called Russellian monism, at the cost of a slippage: Russell, who adopted neutral monism in 1921 after long opposing it, holds the stuff to be neutral, that is, neither mental nor physical, where several of his heirs people it with the experiential properties he refused.

The Analysis of Mind (1921) · The Analysis of Matter (1927)

Mind and body are not two things in relation, but one and the same thing expressed under two attributes, the order of ideas following exactly that of things. The human mind is the idea of the body, neither produced by it nor able to act upon it, which dissolves the Cartesian question of their interaction instead of answering it. Spinoza adds that all individuals are animate in varying degrees, thought being no privilege of brains: this is the historical matrix of dual-aspect monism, and the acknowledged ancestor of contemporary panpsychism.

Ethics, II, props. 7 and 13 (scholium) · Ethics, III, prop. 2

Smart argues that sensations are not merely correlated with brain processes: they are identical to them, as lightning is an electrical discharge. This identity theory rests on a principle of economy: if everything else in the living world is explained in physico-chemical terms, making consciousness the sole exception would force us to admit dangling laws, with no role in the edifice of science. It is objected that one can know one's own sensation while knowing nothing of the brain: he answers with a topic-neutral analysis, saying "I have an orange after-image" amounting only to saying that something is going on in me like what goes on when I see an orange. The statement says nothing of the nature of that "something", and nothing forbids its being a brain process.

"Sensations and Brain Processes" (1959) · Philosophy and Scientific Realism (1963)

The soul is corporeal: an assembly of very fine atoms that dissolves at death like the rest. Thought and sensation are material processes, with nothing immortal or immaterial.

Epicurus, Letter to Herodotus; Lucretius, On the Nature of Things, III

Searle holds consciousness to be an ordinary biological phenomenon, on a par with digestion or photosynthesis: it is caused by low-level neuronal processes and realized in the brain as a higher-level property. That a state is lived in the first person does not entail that it is immaterial: its mode of existence is subjective, its nature remains biological. This biological naturalism refuses both inherited camps, the dualism that makes mind another substance, and the materialisms that, to save objectivity, end up treating lived experience as negligible. His critics reply that an irreducibility of principle brings him despite himself close to property dualism: he disputes this by distinguishing causal reduction, which he grants since the brain does produce consciousness, from ontological reduction, which would delete the first-person point of view instead of explaining it. This is what settles his place here: the irreducibility he maintains is indeed that of the subjective character of experience, which he holds to be a first-person ontology, but it does not make consciousness a property added to the brain. For him consciousness is a way the brain itself is, at a higher level, not one more ingredient in the inventory of the world.

"Minds, Brains, and Programs" (1980) · The Rediscovery of the Mind (1992)

Dennett rejects qualia as the tradition conceives them: intrinsic, ineffable, private and infallible properties, given to introspection. What exists are brain states and the real patterns to which our reports attach; introspection is not a gaze upon an inner stage but a source of reports, often confabulated, which his method, heterophenomenology, treats as data to be explained rather than as established facts. Consciousness is therefore not denied: it is the appearance of an inner glow that itself becomes the effect to be explained.

"Quining Qualia" (1988) · Consciousness Explained (1991)