1. The Identity Theory

2. Ancient Views of the Brain
Aristotle thought the function of the brain was to cool the blood. Nowadays we tend to think that the brain’s primary purpose is for thinking.

3. The Identity Theory
The Identity Theory says that mental states are physical states of the brain. Cf. Property dualism, which says they are non-physical states of the brain.

4. Clarification
The Identity Theory says that all mental states are brain states. It does not say that all brain states are mental states. We might characterize it: certain brain states are mental states.

5. Brain States
Mental States

6. More Specific Claims
Conscious visual perception = high levels of neural activity in V1. Experience of pain = C-fibers firing. Type of mental state = type of brain state.

7. J. J. C. Smart
J. J. C. Smart is one of the best- known 20th Century identity theorists. At the beginning of his career he was a behaviorist, but later defended the Identity Theory.

8. Smart’s Analogy
For Smart, the claim Mental states are brain states. was a lot like the claims: Water is H2O. Lightining is an electrical discharge.

9. Smart’s Analogy These identities are: Not obvious
Not easily discovered
Not part of the meanings of the words
(Compare “Bachelors are unmarried men,” or “Hens are female chickens.”)

10. Type vs. Token

11. Type vs. Token

12. Examples “Scientists have discovered a 10,000 year old fish.”
“Dinosaurs are extinct.”
“I have hundreds of foreign coins.”

13. Types and Properties
Standardly, types and properties are considered to be the same thing. The type dog = the property of being a dog. Tokens of a type are specific instances: things that have those properties.

14. Type Identity Theory
Type identity theory claims that mental properties (mental states) are identical to properties of brains (brain states). The property of being water = the property of being H2O. The property of being a mental state = the property of being (certain) brain states.

15. Token Identity Theory
(Token identity theory is more difficult to understand. We’ll talk about it next time.)

16. Arguments for the Identity Theory

17. Causal Powers
Many mental states are caused by events in the world around us. The visual impressions we get when we open our eyes and look around are an example. Additionally, many of our mental states can cause us to take actions. If you see something flying at your head, that may cause you to move out of the way.

18. Nomological Danglers
One early identity theorist, Herbert Feigl, coined the term “nomological dangler” for the interactions a non-physical mind had with the world.

19. MSs Caused by States of the World
According to the Identity Theorist, the fact that mental states are caused by states of the world is the same fact as the fact that brain states are caused by states of the world.

24. Some MSs Cause Actions
For the Identity Theorist, this is the same as the claim that certain brain states cause actions. Again, the evidence for this is very strong.

27. Some MSs Cause Other MSs (In Reason-Respecting Ways)
We can tell from what we’ve already seen that brain states cause other brain states. But can the identity theorist explain why these processes are rational/ logical?

28. Evidence from Deficit Studies

29. Phineas Gage

31. From Ravenscroft

32. While he was recovering, his family says he amused his nieces and nephews by making up fun stories.
A doctor did say he was changed– while he was recovering. But he said he was fine afterward.
He did lose his job– because his old employer wouldn’t take him back when he was better.

33. Later in his life a doctor said Gage experienced ‘no impairment whatsoever.’
Gage did die early– but that’s because he experienced severe brain trauma.
No credible report says that he was an alcoholic or irresponsible.

35. Expressive Aphasia
Broca’s aphasia (expressive aphasia) results from damage to Broca’s area. Here, patients can understand language perfectly, but can’t produce it. Here’s one patient explaining why he was at the hospital: “Yes... ah... Monday... er... Dad and Peter H... (his own name), and Dad.... er... hospital... and ah... Wednesday... Wednesday, nine o'clock... and oh... Thursday... ten o'clock, ah doctors... two... and doctors... and er... teeth... yah.”

36. Video Time!