Computational Functionalism Motivations A functionalist general purpose inputoutput

Computational Functionalism

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

Turing Machine n Turing machines consist of: n n an infinite tape divided into squares a head that reads from and writes to the tape a finite set of internal states; q 0, …, qn a finite alphabet; b 1, …, bm

Turing Machine 1 q 0 q 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 q 0 + 1 1 # #

Turing Machine 1 q 0 q 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 q 0 + 1 1 # #

Turing Machine 1 q 0 q 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 q 0 + 1 1 # #

Turing Machine 1 q 0 q 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 + q 0 1 1 # #

Turing Machine q 0 q 1 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 # # q 0

Turing Machine q 0 q 1 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 # # q 0

Turing Machine q 0 q 1 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 # # q 0

Turing Machine q 0 q 1 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 # # q 1

Turing Machine q 0 q 1 1 1 Rq 0 #Halt + 1 Rq 0 # #Lq 1 # # 1 1 1 # # # Halt

Turing Machine 1 + # q 0 q 1 #Rq 1 1 Halt # # 1 1 1 + 1 1 # # q 0

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

Psychology n Instrumentalism A theory predicts n Realism A theory explains

Difficulties n Identity What does it means for A to have the same mental state as B? n q 0 is only definable as the triplet: {<1, 1 Rq 0>, <+, 1 Rq 0>, <#, #Lq 1>} n Each state is defined in terms of the other states n Different psychologies can’t even be compared n

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

Turing Test n If a machine passes a test that we think could only be passed by a thinking then we have no grounds to deny that the machine is thinking. n 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 n Searle thought that the idea that mental states could be identified with computational states was almost demonstrably incorrect.

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

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

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

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