Functionalism Computational Role

Motivations A functionalist general purpose input-output device certainly sounds like a computer Mind does informational things A machine implementation of functionalism is natural Computational functions are multiply realisable

Turing Machine Turing machines consist of: an infinite tape divided into squares a head that reads from and writes to the tape a finite set of internal states; q0, …, qn a finite alphabet; b1, …, bm

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    +    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    +    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    +    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    +    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    1    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    1    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    1    1   1   #   #  q0

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    1    1   1   #   #  q1

Turing Machine q0 q1 1 1Rq0 #Halt + # #Lq1 #    #    1   1    1    1    1   #   #   #  Halt

Turing Machine q0 q1 1 #Rq1 1Rq1 + 1Halt # #    #    1   1    1    +    1   1   #   #  q0

Machine Functionalism The computational functionalist claim is that the mind can be thought of as a TM Mental states of Stephen are to be identified with the internal states of Stephen’s TM

Psychology Instrumentalism A theory predicts Realism A theory explains

Difficulties Identity What does it means for A to have the same mental state as B? q0 is only definable as the triplet: {<1, 1Rq0>, <+, 1Rq0>, <#, #Lq1>} Each state is defined in terms of the other states Different psychologies can’t even be compared

Difficulties Simulation Do we think that a weather simulation program actually has weather going on inside it?

Turing Test If a machine passes a test that we think could only be passed by a thinking thing then we have no grounds to deny that the machine is thinking. Have a conversation with A and B, one of them a machine, the other a person. If you can’t tell which is the machine then both are thinking.

The Chinese Room Searle thought that the idea that mental states could be identified with computational states was almost demonstrably incorrect.

The Chinese Room Responses System The room + the man + … understands Reply Let him memorise it all

The Chinese Room Responses Robot Connect the room to the world Reply What is the robot really receiving?

The Chinese Room Responses Simulator Make the room look like the brain Reply Where’s computation now?

The Chinese Room Searle thinks that only  machines can think, ie. brains, but not by computing.