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24.09 spring 061

24.09 Minds and Machinesspring 2006

• handout onfunctionalism

• problem set, writingassignment this week

• final exam 5/24 9-12• current week

highlighted

24.09 spring 062

24.09 Minds and Machinesspring 2006

• functionalism,contd.

24.09 spring 063

“troubles with functionalism”

Imagine a body externally like a human body, sayyours, but internally quite different. The neuronsfrom sensory organs are connected to a bank oflights in a hollow cavity in the head. A set ofbuttons connects to the motor-output neurons.Inside the cavity resides a group of little men.Each has a very simple task: to implement a“square” of an adequate machine table thatdescribes you. (96)

24.09 spring 064

Block’s homunculus head

G

M

I16 I17 I18

stateG-man

input

O5CO77ZO8H H

O45PO191MO25K G

I18 117 I16. .O190 O191

input

state

output

24.09 spring 065

there is prima facie doubt whether [thehomunculus head] has any mental states atall—especially whether it has what philosophershave variously called “qualitative states”, “rawfeels”, or “immediate phenomenologicalqualities”…there is prima facie doubt whetherthere is anything it is like to be the homunculi-headed system. (97)

24.09 spring 066

from the philosophical toolkit:

a priori and a posteriori• (knowable) proposition p is knowable a priori iff p

can be known independently of experience• otherwise, proposition p is knowable (only) a

posteriori

a posteriori andcontingent:

it’s sunny

a posteriori andnecessary:

water=H2O

a priori andcontingent:

??

a priori andnecessary:

2+3=5

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24.09 spring 067

Functionalism vs.psychofunctionalism (see Block)• suppose functionalism is true• could you (at least “in principle”) write down the

functional characterization of mental states just byreflecting on the meanings of mental vocabulary?

• the (“commonsense”, “analytic”) Functionalistsays ‘yes’

• the (“scientific”, “empirical”) psychofunctionalistsays ‘no’—science will tell us the functional story,not conceptual analysis

24.09 spring 068

Functionalists andpsychofunctionalists

• Lewis and Armstrong are Functionalists (“analyticfunctionalists”)

• Putnam is a psychofunctionalist• psychofunctionalism is probably the more popular

version• we will return to this issue when we discuss

Chalmers’ paper “Consciousness and its Place inNature”

24.09 spring 069

“mad pain and martian pain”

• defends Functionalism—the functionalspecifications of mental states can benoodled out from the armchair

• defends “realizer state” as opposed to“role state” functionalism

• replies to the “knowledge argument” (to bediscussed later)

24.09 spring 0610

his pain is caused bymoderate exercise

the madman

intense pain causeshim to snap hisfingers

24.09 spring 0611

the martian

• his hydraulic mindcontains nothing likeour neurons

• the causes and effects ofhis pain are like thecauses and effects ofour pain

24.09 spring 0612

• a simple identity theorysolves the problem of madpain, but not martian pain

• a simple functionalism goesthe other way: right aboutthe martian, wrong about themadman

• Armstrong’s and mytheory…wriggles betweenScylla and Charybdis

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24.09 spring 0613

• the concept of pain is the concept of astate that occupies a certain causal role

• whatever state (e.g. c-fibers firing) doesoccupy that role is pain

• but something else might have occupied therole (just as someone other than SusanHockfield might have occupied the MIT-president role)

• so, pain might not have been pain• ‘pain’, as Armstrong and I understand it, is a

nonrigid designator

24.09 spring 0614

the martian

• the thing to say about martianpain is that the martian is inpain because he is in a statethat occupies the causal role ofpain for martians (hispopulation)

• ditto (mutatis mutandis) for us

24.09 spring 0615

the madman is in painbecause he is in thestate that occupies thecausal role of pain formankind

he is anexceptionalmember of thatpopulation

the state thatoccupies the rolefor the populationdoes not occupy itfor him

24.09 spring 0616

Minds and Machinesspring 2006

read Putnam, Burge