10/26/13

1

Rigidity & Necessity

•  If Kripke is right, Identity Theory (ID) is necessarily true if true at all.

•  This is a consequence of assuming that mental terms refer to natural kinds rigidly (=mental phenomena like pain are natural kinds whose names are rigid designators).

•  It follows that if pains = C-fiber-firings, then this is a metaphysical necessity.

1

Chauvinism

•  So, nothing can be a pain unless it’s a C-fiber-firing. •  So, there is no possibility of making pain feeling sentient

and intelligent robots or androids without using c-f-f. •  Similarly, if we come across other sentient and intelligent

species composed of different material, they can’t by necessity feel pain, even if they may otherwise be functionally identical to humans.

•  So only humans are capable of feeling (pains, itches, etc) •  ID, therefore, implies human chauvinism: only creatures

with similar biology and physiology can have mentality!

2

10/26/13

2

Multiple realizability of mental states and events (=mental kinds or properties)

•  Our ordinary concepts of mental phenomena seem not to put any constraints on the internal constitution of these phenomena.

•  Think of angels, ghosts, souls. Whether or not you believe they actually exist. We seem to have no difficulty conceiving them as existing. But they have minds (or are minds) that are not even physically constituted.

•  Similarly, we have no difficulty conceiving super computers or androids that are capable of having genuinely mental characteristics.

•  Our concepts of mental kinds clearly allow for these kinds to be multiply realized in different media.

•  Mental states/kinds/processes are multiply realizable.

3

Functionalism about mousetraps

•  A lot of kinds or properties are functional kinds in that they are multiply realizable.

•  What is a mousetrap? •  Anything that has a certain function, anything with a

causal job description. •  A mousetrap is any device with a property that enables it

to either trap and hold a mouse or kill a mouse. •  There are indefinitely many token devices that will fulfill

this function.

4

10/26/13

3

Realizers of the property of being a mousetrap

5

6

10/26/13

4

7

8

10/26/13

5

9

10

10/26/13

6

11

12

10/26/13

7

13

14

10/26/13

8

15

Functional properties

16

Kim defines a functional property thus:

10/26/13

9

Realization

17

Kim, then, defines the relation of realization thus:

18

Functionalism

•  Central to any version of functionalism is the idea that a mental state can be characterized in terms of the input-output relations it mediates, where the inputs and outputs may include other mental states as well as sensory stimuli and physical behaviors.

•  Mental phenomena are conceived as nodes in a complex causal network that engages in causal transactions with the outside world by receiving sensory inputs and emitting behavioral outputs.

10/26/13

10

Behaviorism

•  Analytical (or, Philosophical) Behaviorism: mental terms can be defined solely in terms of complex patterns of stimulus/response relations along with their histories or in terms of dispositions to conform such S/R patterns. (logical positivists such as Hempel, early Carnap, etc.)

•  Metaphysical Behaviorism: mental kinds are nothing but complex patterns of dispositions to behave in certain ways under such and such stimulus conditions. (Late Wittgenstein, Ryle, and most logical positivists)

•  Methodological Behaviorism: Scientific psychology is the study of behavior solely in terms of S/R patterns and their reinforcement histories. (most behaviorist psychologists of the early 20th cc, such as Watson and Skinner)

19

Functionalism and Behaviorism

•  Each type of mental state is a state consisting of a disposition to act in certain ways and to have certain mental states, given certain sensory inputs and certain mental states.

•  This is like behaviorism except that there is no restriction against adverting to inner mental causes in addition to perceptual input and behavioral output.

•  Various versions of functionalism: –  Machine functionalism –  Causal-role functionalism

20

10/26/13

11

Causal-Role Functionalism

•  A mental type can be characterized in terms of the input-output relations it mediates, where the inputs and outputs may include other mental states as well as sensory stimuli and physical behaviors.

•  Mental phenomena are conceived as nodes in a complex causal network that engages in causal transactions with the outside world by receiving sensory inputs and emitting behavioral outputs.

•  Ramsey-Lewis technique of specifying causal/functional roles: Ramseification

(after Frank P. Ramsey 1903 – 1930)

21

22

A toy example: 4-sentence theory of pain

•  (T) For any x: 1.  if x suffers tissue damage and is normally alert, x is in pain; 2.  if x is awake, x tends to be normally alert; 3.  if x is in pain, x winces and groans and goes into a state of

distress; and 4.  if x is not normally alert or x is in a state of distress, x tends to

make more typing errors.

•  T describe lawful regularities (or causal relations). [This is what Lewis calls “the Postulate of Theory T”

•  The (blue) italicized expressions are nonmental predicates (O-terms] designating observable physical, biological, and behavioral properties;

•  the expressions in (maroon) boldface are psychological expressions [T-terms] designating mental properties.

10/26/13

12

23

Ramseification of theories

•  We first "Ramseify" T by "existentially generalizing" over each mental expression occurring in T:

•  (TR) There exist states M1, M2, and M3 such that: for any x,

1.  if x suffers tissue damage and is in M1, x is in M2; 2.  if x is awake, x tends to be in M1; 3.  if x is in M2, x winces and groans and goes into M1; and 4.  if x is either not in M1 or is in My, x tends to make more

typing errors.

•  TR, instead of referring (as T does) to specific mental states, speaks only of there being some states or other, M1, M2, and M3, which are related to each other and to observable physical-behavioral states in the way specified by T.

•  T implies TR.

24

Ramsey-Lewis Technique for defining mental terms

•  Abbreviate TR as “ ∃ M1, M2, M3 [T(M1, M2, M3)] " –  This is “the Ramsey sentence of T” (The symbol ∃, called the "existential quantifier,” is read: "there exist") –  “ ∃! M1, M2, M3 [T(M1, M2, M3)] " is the Modified Ramsey

sentence of T (read the symbol ∃! as “ there uniquely exist”)

Definitions of “pain”, “distress”, “normally alert”: •  x is in pain = ∃ M1, M2, M3 [T(M1, M2, M3)] and x is in

M2. •  X is in distress = ∃ M1, M2, M3 [T(M1, M2, M3)] and

x is in M1. •  x is normally alert = ∃ M1, M2, M3 [T(M1, M2, M3)] and

x is in M3.

•  No circularity problem remains if we define the mental terms all at once!

10/26/13

13

25

The Choice of Underlying Psychological Theory

•  Common sense (folk) psychology as an implicit theory ==> Common sense functionalism, or simply Functionalism [this is Lewis’ position]

(Like Logical Behaviorism, this is both a semantic and ontological theory)

•  Scientific psychological theory ==> Psychofunctionalism [Fodor’s position] (Only ontological theory)

The truth of these theories depends on their generalizations!

26

Behaviorally Adequate Theories

•  Let us assume that psychological theories posit internal states to systematize correlations between sensory inputs and behavioral outputs. These internal states are the putative psychological states of the organism.

•  Suppose now that each of two theories, T1 and T2, gives a correct systematization of inputs and outputs for a given psychological subject S, but that each posits a different set of internal states. That is, T1, and T2 are both behaviorally adequate psychologies for S, but each attributes to S a different internal psychological mechanism that connects S's inputs to its outputs.

•  Is there some further fact about these theories, or about S, that determines which (if any) is the correct psychology of S and hence the theory to be Ramseified to yield causal-functional definitions of mental states?

10/26/13

14

27

Functionalism as Physicalism

(P) The states that the Ramseified psychological theory, TR, affirms to exist are physical-neural states; that is, the variables, M1, M2, . . . of TR and in the definitions of specific mental states range over physical-neural states.

•  A functionalist who accepts (P), that is, a physicalist functionalist, will interpret the ontology of our original, un-Ramseified psychological theory in an analogous way: The internal states posited by a correct psychological theory are physical-neural states.

28

Objections and Difficulties

•  The QUALIA Problem –  The possibility of inverted spectrum –  The possibility of absent qualia

•  Problem of causal powers –  Disjunctive properties ?

•  Homonculi-headed robots (Ned Block)

10/26/13

15

29

Inverted Spectrum (IS)

“RED APPLE”

“RED APPLE”

Mr. Normal

Mr. Invert

(Both truly apply to the apple?)

30

Roles Versus Realizers: The Status of Cognitive Science

•  Realizer Functionalism: My experiencing pain at time t is identical with my C-fibers being activated at t (where C-fiber activation is the pain realizer in me); the octopus's experiencing pain at t is identical with its X-fibers being activated at t (where X-fiber activation is the octopus's pain realizer); and so on.

•  Role Functionalism: My experiencing pain at time t is identical with my being at t in a state that plays causal role R (that is, the role of detecting bodily damage and triggering appropriate behavioral responses); the octopus's experiencing pain at t is identical with its being, at t, in a state that plays the same causal role R; and so on.

10/26/13

16

31

How to drive psychophysical identities (Lewis)

1.  Mental state M = The occupant of causal role R (by definition of M)

2.  Neural state N = The occupant of causal R (by the physiological theory)

3.  Therefore: Mental state M = Neural state (N) (by transitivity of =)