INTERIM EXAM 2
Lecture 7: Denny Borsboom
The problem of consciousness
The mind-body problem
The mind-body problem
The dualist René Descartes (1596-1650).
The materialist: Thomas Hobbes (1588-1679).
-isms…
Monism (“there is only one kind of things”)
Materialism (‘ultimately everything is material’)
Idealism (‘ultimately everything is mental’)
Dualism (“there are two kinds of things”)
Substance-dualism (‘mind and body are kinds of distinct entities’)
What is the thing that leads to monism & dualism?
Dualism
René Descartes (1596-1650)
Descartes views the body, but not the mind, as a machine. Mind and body must therefore be
different entities. Descartes’ reasoning produces the mind-body problem. However, the idea that the
mind is a causal director of the body gets ever more problematic.
Descartes believed that sensory information was transferred to the mind through the pineal gland.
Mental misery…
Causal effects of the mind are obscure. Interaction problem: how can a non-material entity cause
physical events? Causal closure problem: if every physical event has a physical cause, where does the
mind enter? How about the law of conservation of energy? Brain damage problem: why would a
nonmaterial entity react to brain damage?
Nowadays, no theory can afford to be inconsistent with established scientific theory without
answering for it.
The teleportation test: do we even understand the idea of an immaterial mind? Where is it when
you’re asleep? Or suppose you’re teleported to the moon - does your mind travel with you or not?
And what if your Earthly body accidentally fails to be destroyed - are there then two you’s?
Thinking about mind and body as separate entities looks easy. However, as soon as we ask the
question ‘how would that work?’ it turns out we don’t really have a decent answer. The inability to
provide a reasonable theory of mind-body interaction has led to demise of dualism in scientific
articles.
Materialism
The materialist maintains that, in the end, there is only matter. The concept of ‘matter’ is however
quite flexible (so fields, states, processes, functions, etc. all count as ‘material’). Most important is
that the mind, whatever it may be, is a part of nature and observes the laws of nature. This still
leaves many possibilities for exactly what the mind is.
The problem of consciousness
The materialist doesn’t have an easy life either. Without a mind, it’s hard to explain how and why we
have conscious mental states. Three problem areas:
o Mental states (or not)
o Reductionism (or not)
o Subjective experience (or not)
,Mental states:
In daily life, mental states (‘to want ice cream’, ‘knowing where they sell ice cream’) explain
behaviour (‘buying ice cream’). This is called belief-desire psychology and is part of folk psychology -
but also of scientific psychology. This kind of explanation surfaces throughout psychology (social,
clinical, development…). The theory of planned behaviour from Ajzen.
How can mental states receive a respectable place in scientific explanation of human behaviour? If
the mind does not exist as a distinct substance, then how can mental states exist at all? Or is it all just
spooky stuff, and is the only good mental state an eliminated mental state?
o Eliminative materialism
One option is to deny the existence of mental states: eliminative materialism. Mental states aren’t
real and will not appear in the ‘ultimate description of the universe’. Folk psychology is just like naïve
physics: in the end it will disappear. The philosophical couple Paul & Patricia Churchland are
eliminative materialists. It just takes some getting used to.
Eliminative materialism is a bridge too far for most scientists. Mental states appear too important for
the explanation of behaviour to dismiss them. It is also unclear what should take the place of
ordinary ‘belief-desire’ explanations of behaviour - neuroscience that can do this is currently science
fiction. Elimination seems premature; throwing out an explanation before you have a new one.
Because right now, we don’t have a right measure to be able to explain mental states etc. through
imaging techniques.
How do psychological states relate to brain states then? Two most important routes; non-reductive
& reductive materialism.
o Reductive materialism
Materialism with mental states. Non-eliminative materialism. One can deny that the mind exists as a
substance, but still make room for mental states. To do this, one must produce an account of how
mental states are rooted in brain states. Identity theory and functionalism are related attempts to do
this.
Identity theory
Maintains that mental states are brain states. To want an ice cream = brain state X. Identity theory
was developed to keep a causal role for mental states (not to deny it). ‘John bought an ice cream
because he wanted one’ is true, but really means ‘John bought an ice cream because he had brain
state X’. Mental state is the brain state, it isn’t produced by the brain state. They are the same. Very
strong position. Very nice, very strong, very clear. Sharp. But also difficult. Two different types of
identity.
- Type-type identity. But… what is identical to what? Strong answer: types of mental states are
identical to types of brain states across individuals and time points. This implies a one-to-one
mapping of mental states to brain states. If this holds true, then a full reduction of
psychology to neuroscience is a realistic possibility. A reductionist isn’t necessarily the same
as a materialist. Not all materialists are reductionists.
Reductionism
Step 1: start with a scientific law in the higher order science (the science to be reduced, e.g.
psychology).
Step 2: establish bridge laws: one-to-one correspondence relations between terms in the higher
order science and terms in the lower order science (the reducing science, e.g. neuroscience).
Step 3: show that the higher order law follows from laws of the reducing science given the bridge
laws.
The most famous reduction in the history of science is the reduction of the ideal gas laws to statistical
mechanics through the bridge law ‘temperature = mean kinetic energy’. Very powerful, but very rare.
, Most researchers think type-identity theory is too strong: neural plasticity implies that the same
mental functions can be performed in different ways. Individual differences in physical makeup
suggest that brains may be quite heterogeneous, especially at the fine grained level of patterns of
neural connections. Mental states are often defined by their contents, and that content is very likely
to be encoded in many different ways.
The teleportation test: suppose your mental states are your brain states. Can you have the same
thought twice? And what about teleportation: your replica has a different brain, so are its brain
states different? That would mean you can’t really be teleported at all… the destruction of your body
on earth is murder!
o Non-reductive materialism
Also with mental states, but non-reductionist. Functionalism and the computer metaphor. The mind
can run on different brains. If that’s the case, different computers can run the same software with
different hardware. Define things through their role: function.
Functionalism and multiple realizability
Functionalism and the computer metaphor. The computer metaphor extends the Turing machine
into the domain of the human mind: mind:body = software:hardware. The mind is a program that
‘runs on’ the brain. Just like the variables in a computer program, mental states are characterized by
their function, not their realization.
The Turing machine can implement all computable functions. This includes logic; hence the Turing
machine can ‘think’ in a basic way. A Turing machine can be made of many different kinds of
materials: it is multiple realizable. What if mental states are just like software states, in which
function is enough to characterize them, while their physical realization is unimportant?
Functionalism
Functionalism defines mental states in terms of their role. For instance: realizing input-output
relations. Fear of spiders = whatever state causes people to avoid spiders, to say they are afraid of
spiders, etc. In this view, fear of spiders is not caused by the brain, but realized in the brain.
Multiple realizability: computational level = John gives Jane 10 euros. Implementation level = 10 coins
of 1 euro, 1 bank note of 10 euros, wire transfer, credit-card,… Same goes for the brain: scared of
mice because they carry diseases / because you believe they’ll rule the world. Different brain activity.
Idea of things being defined to their function isn’t that strange at all, because we see it with money
as well. Maybe not so strange that it goes for the brain as well.
Realization versus causation.
Money is one of the best examples of multiple realization. A ten euro bill is a ten euro bill because
you can buy certain things with it, not because of what it’s made of. So it plays a certain role in our
social, psychological and economic system. However, whether it’s made of paper or of iron doesn’t
matter. Important: the ten euro bill is not caused by the paper, because it does not exist
independently of that paper. Instead, the paper realizes the ten euro bill. Functionalists think that
mental states exist in precisely this way. Just like money, they are defined in terms of their role, and
realized in the brain. If you want to learn how Windows works, you don’t have to understand the
chips etc. in your computer.
Identity theory, version II: token-token identify
Type-type identity is killed by multiple realizability. No longer a 1-to-1 mapping of brain states to
mental states. But a many-to-1 mapping of brain states to mental states. But… what if ‘to want an
ice cream’ = ‘brain state x for John’, brain state y for Jane, brain state z for Jerry, etc… Then we do
have identity of brain states with mental states. This is called token identity theory.
