Question 4: Identity & Kripke

Question 1

Identity Theory

Answer 1

Mental states are physical states of the brain. Something is in pain only if, and because, its c-fibers are firing.

Question 2

Kripke’s Argument

Answer 2

1) x is identical to y (assume)
2) y is necessarily identical to y
3) So, x is necessarily identical to y
4) So, if (1), then (3)
5) Therefore, for any x & y, if x is identical to y, then x is necessarily identical to y

Question 3

Premise (2) of Kripke’s Argument

Answer 3

2) y is necessarily identical to y

Any one thing is identical to itself.

Question 4

Premise (3) of Kripke’s Argument

Answer 4

3) So, x is necessarily identical to y

Leibniz law

Question 5

Premise (4) of Kripke’s Argument

Answer 5

4) So, if (1), then (3)

Conditional proof

Question 6

The Modal Argument

Answer 6

1) If the identity theory is correct, then pain is identical to c-fiber firing
2) If pain is identical to c-fiber firing, then pain is necessarily identical to c-fibers firing.
3) If pain is necessarily identical to c-fibers firing, then pain couldn’t have existed without c-fibers
4) Pain could have existed without c-fibers
5) So, the Identity Theory is incorrect

Question 7

Premise (1) of the Modal Argument

Answer 7

1) If the identity theory is correct, then pain is identical to c-fiber firing
explain: definition of identity theory

Question 8

Premise (2) of the Modal Argument

Answer 8

2) If pain is identical to c-fiber firing, then pain is necessarily identical to c-fibers firing.

Question 9

Premise (3) of the Modal Argument

Answer 9

3) If pain is necessarily identical to c-fibers firing, then pain couldn’t have existed without c-fibers
explain: By definition of necessity

Question 10

Premise (4) of the Modal Argument

Answer 10

4) Pain could have existed without c-fibers