Mind–body problem

How mental and physical phenomena are related, given that neither an identity nor a separation between them survives inspection.

Theme: Mind, self and consciousness
Tradition: Western
Term fixed: 1641

In plain terms

A drug alters a mood. A decision moves an arm. Nothing is more familiar, and no account of how it works commands agreement.

If mind and body are two different kinds of thing, then something non-physical is pushing physical matter around, and the physics has no room for the push. If they are one kind of thing, then experience has to be identical to some physical process, and no description of a process seems to say anything about what it feels like.

Both horns are uncomfortable, which is why the problem survives. It is not a puzzle awaiting a discovery so much as a knot in how the two vocabularies fit together - and the strongest evidence that it is a real knot is that every proposed solution is rejected by most people who work on it.

As a philosopher would put it

Descartes's substance dualism generates the interaction problem immediately, pressed hardest by Elisabeth of Bohemia: how does an unextended thing move an extended one. The historical responses - occasionalism, parallelism, Spinoza's one substance with two attributes - are all attempts to keep the distinction while dropping the causation.

The modern positions divide over causal closure. If every physical event has a sufficient physical cause, then a distinct mental cause is either redundant or the closure is false. Epiphenomenalism accepts redundancy, at the cost of making experience causally idle. The identity theory and functionalism accept closure by making mental states physical or functional, at the cost of the explanatory gap.

Property dualism keeps one substance and two kinds of property, and inherits the exclusion problem in a new form. Panpsychism responds by putting experience in at the bottom rather than deriving it, which avoids emergence and raises the combination problem instead - how micro-experiences would compose into one. Every option pays somewhere, which is the shape of a genuine impasse rather than an unfinished inquiry.

Where you meet it

Deep brain stimulation for Parkinson's disease places electrodes in the subthalamic nucleus and delivers current continuously. It is a routine and highly effective treatment for motor symptoms, performed thousands of times a year.

It also, in a minority of patients, changes things nobody was treating. Documented effects include new impulsivity, gambling and hypersexuality, and in some series a flattening of mood; adjusting stimulation parameters can bring them on and take them away within minutes, in the clinic, while the patient is awake and talking.

A neurologist turning a dial and watching a personality shift is not settling anything philosophical. Both dualists and physicalists predict correlation, and correlation is what is observed. What the case does is put the problem where it cannot be treated as academic: someone has to decide whether the person under stimulation is more themselves or less, and the ethics literature on that question has no more resolution than the metaphysics does.

What is actually disputed

Whether the problem is real or an artefact of how it was posed.

One view is that Descartes created it by starting with two substances, and that a sufficiently good account of the mental as embodied and enacted makes the gap disappear rather than closing it. Another is that the gap is a permanent feature of our cognitive situation - McGinn's position, that we are constitutionally unable to grasp the link, in the way that a dog cannot grasp arithmetic.

What almost everyone concedes is that no current position is comfortable. Physicalism owes an account of why there is experience; dualism owes an account of interaction; panpsychism owes the combination problem; eliminativism owes an explanation of why the illusion is so complete. The persistence of that standoff for four centuries is itself the strongest evidence about the shape of the question.

Commonly confused with

the hard problem The hard problem is specifically about why there is experience at all. The mind-body problem is broader and includes causation, which is a separate difficulty.
the brain-mind relation in neuroscience Neuroscience maps correlations, and both sides of the philosophical argument predict correlations. The dispute is about what the correlation is a correlation of.

Defined against

Matter The problem exists because the two terms were defined so as to have nothing in common

Philosophers

René Descartes Two substances, and the interaction problem that follows
Baruch Spinoza One substance under two attributes, and no interaction to explain
Gottfried Wilhelm Leibniz Pre-established harmony rather than causal contact
George Berkeley Removes the body side entirely
Maurice Jean Jacques Merleau-Ponty Rejects the framing: the lived body is neither term

Works

Meditations on First Philosophy Where the modern problem is created
Ethics The one-substance answer
Monadology Harmony without interaction
The Concept of Mind The category-mistake diagnosis
Phenomenology of Perception The attempt to dissolve the pair through the body

Schools

Cartesianism The source of the modern form
Spinozism One substance, two attributes
Phenomenology Where the framing itself is rejected
Vienna Circle Where the question was declared a pseudo-problem
Process Philosophy Where experience is put in at the bottom

Related concepts

Mind c. 450 BC · Consciousness 1641 · Qualia 1929 · Embodiment 1945 · Emergence 1875

Descartes did not invent the question but he created its modern form, by making mind and body two substances with nothing in common and then having to explain how they interact.