Physicalism

Transcription

1 Physicalism

2 Table of contents 1 What is Identity Theory? 2 Closure of Physics and the Unity of Science Supervenience 3 Argument From Agency 4 Arguments From Causal Overdetermination

3 Identity Theory Physicalism Two descriptions of the same thing. (Clark Kent and Superman; lightning and electricity) Opacity Not conceptual, but empirical Why believe this position? It s supposed to be made plausible by scientific advances....

4 Table of contents 1 What is Identity Theory? 2 Closure of Physics and the Unity of Science Supervenience 3 Argument From Agency 4 Arguments From Causal Overdetermination

5 Closure What do these mean? Causal Closure of Physics Every physical event has sufficient physical causes. Sufficient?

6 Unity of Science Unity of Science The world comes in layers or levels, e.g., the level of physics, of biology, of psychology, of sociology, of political science, etc. These different sciences study objects of differing complexity, where the more complex objects are realized in the simpler ones; they are all unified by having all their objects realized in those of fundamental physics. Realized in? What the Unity of Science does NOT say. (It is not about theory reduction.)

7 Why believe these? Carruthers: these are methodological hypotheses in current/recent science C. cites scientific evidence for Closure; what is he thinking of? Here s some speculation: e.g., MRI stuff.

8 Table of contents 1 What is Identity Theory? 2 Closure of Physics and the Unity of Science Supervenience 3 Argument From Agency 4 Arguments From Causal Overdetermination

9 Supervenience here s a way to think about this: supervenience. Supervenience There is no change in the supervening thing without a change in the supervenience base. An example: lite brite

10 Lite Brite

11 Supervenience cont. Supervenience and causation/realization. Supervenience shouldn t be left a mystery. One way to account for it is to posit realization relationships.

12 The Normal Picture Plenty of causation both in the mind body and body mind direction. Examples: perception, decision-making. (Draw a picture.) But: this is ruled out by Closure. For Closure says that there is no P with no P cause....

13 Table of contents 1 What is Identity Theory? 2 Closure of Physics and the Unity of Science Supervenience 3 Argument From Agency 4 Arguments From Causal Overdetermination

14 Agency, first try 1 If our decisions are to really be decisions, then they must be part of the explanation for our actions. 2 If Closure is right, then a full explanation is given by physical states. 3 Our decisions are really decisions. 4 Closure is right. 5 A full explanation of our actions is given by physical states. 6 So: our decisions are physical states. The argument isn t valid as it stands! For there is a full explanation in physical terms. The argument doesn t rule out the possibility of another explanation in mental terms?

15 Table of contents 1 What is Identity Theory? 2 Closure of Physics and the Unity of Science Supervenience 3 Argument From Agency 4 Arguments From Causal Overdetermination

16 Causal Overdetermination Define causal overdetermination Could the mind-body be like this? (draw the picture) Carruthers: this brings up more problems with agency....

17 Agency, second try Let s phrase this as a reductio ad absurdum: 1 Our decisions are non-physical. (assumed for reductio) 2 If our decisions are to really be decisions, then it must be the case that if we didn t decide to act, we wouldn t act.

18 Agency, second try Let s phrase this as a reductio ad absurdum: 1 The overdetermination theory is right. (assumed for reductio) 2 If our decisions are to really be decisions, then it must be the case that if we didn t decide to act, we wouldn t act. 3 Our decisions are really decisions. 4 If we didn t decide to act, we wouldn t act. 5 If the overdetermination theory is right, then even if we decided otherwise, we would still act in the same way (since the physical is sufficient to determine both physical and mental states). 6 So our decisions aren t really decisions. (contradicts line 3) So we must reject some one of the premises. Carruthers would say: reject 1. What is the problem here? The overdetermination theory removes causal effectiveness from our decisions, since the physical is enough to determine everything.

19 Epiphenomenalism What happens if we simply accept this concequence? menalism Mental states are caused by physical states, but do not have causal influence. (A picture.) Epiphenomenalism is even more open to the argument above!

20 The Dualist Strikes Back The dualist argues that the argument from agency is unsound! If the overdetermination theory (or epiphenomenalism) is right, then even if we decided otherwise, we would still act in the same way (since the physical is sufficient to determine both physical and mental states). But the overdeterminist or the epiphenomenalist can insist that if we had decided otherwise, then the physical would have to be different, too! And so we would have acted differently.... (In fact, this is the natural thing to say for someone who believes the mental supervenes on the physical....)

21 The Dualist Strikes Back, cont. Compare: if the acid hadn t reacted with the base, then the electron exchange would have happened the same way (since the laws of physics are sufficient to determine the physical and chemical events). Clearly not: if the acid hadn t reacted with the base, then the electron exchange wouldn t have happened, either. One way to explain this is that the acid-base reaction and the electron exchange just are the same event with two descriptions. But it is enough if the two event-types have to systematically covary... which is exactly what the supervenience theorist thinks.

22 Downward Causation Define Downward Causation: Downward Causation Mental states are caused by or realized in physical states, but also have causal impact on physical states ( downward ). (Draw a picture.) This is part of the common-sensical view. Has Carruthers given us any reason to reject a variant of the common-sense view, with plenty of overdetermination but no inverse causal black holes?

23 Another argument against overdetermination 1 A theory that posits systematic causal overdetermination posits more causation than necessary to explain events. (Because the overdetermination is systematic, you could just remove a whole bunch of causal relations and have all the same effects remain.)

24 Another argument against overdetermination 1 If a theory posits systematic causal overdetermination, then it posits more causation than necessary to explain events. 2 A theory with downward causation posits systematic causal overdetermination. 3 So, a theory with downward causation posits more caustion than necessary to explain events. 4 If a theory posits more caustion than necessary to explain events, then it is less parsimonious than it a variant that posits less causation. 5 All else equal, less parsimonious theories should be rejected for more parsimonious alternatives. 6 A theory with downward causation should be rejected for an alternative without it. What does all else equal mean? Is all else equal?

25 A Parsimonious Alternative Identity theory collapses all the causal relations. Distinguish type vs. token Identity. Non-reductive Materialism A family of views that claims: all things are physical and mental states cannot be reduced to material states. Reduced? (Does the non-reductive materialist think that are there non-physical mental properties? Carruthers calls this weak dualism and thinks he s also shown this is wrong.) Carruthers: token identity i) preserves physicalism ii) preserves some independence of higher sciences from physics (why?) iii) retains the possibility of our having agency iv) avoids problems with overdetermination.