Philosophical Foundations of Cognitive Science

1. 25/10/2004 PFCS 1 Philosophical Foundations of Cognitive Science Various ��isms�

2. 25/10/2004 PFCS 2

3. 25/10/2004 PFCS 3 Idealism Idealism: �Esse est percipi�=�To be is to be perceived�, Berkeley The mental: Is more fundamental than the physical Is logically prior to the physical Cannot be explained in terms of the physical See also Kant, Hegel, etc.

4. 25/10/2004 PFCS 4 Realism Realism: Real things just are things as philosophy/science/common sense takes them to be, respectively: Scholastic Realism Scientific Realism Na�ve Realism

5. 25/10/2004 PFCS 5 Idealism vs. Realism Idealism vs. Realism What seems right about idealism is inherent in that we are constrained to use our own concepts in investigating the real What seems right about realism is that the answers to the questions we put to the real are provided by reality itself => Naturalised Empiricism (W.V.O.Quine, �Two Dogmas of Empiricism�, �Epistemology Naturalized�): There are no theory independent observations Nevertheless, we can test our conceptual scheme against reality, and improve it

6. 25/10/2004 PFCS 6 Materialism Materialism: A view corresponding to the rise of modern science Essentially, most of the positions that we will be considering in detail in this course are materialist: Behaviourism Identity Theory Functionalism To the extent that the mind can be known, it can be known to be a part of the material universe as understood by science Materialists can either be plain realists (of some sort) or Quinean empiricists

7. 25/10/2004 PFCS 7 Dualism Descartes (1596-1650) was well aware of many early anatomical experiments Nevertheless, for Descartes Mind and Matter were separate types of stuff: �Res extensa� (extended stuff): Matter, with physical extension, and no conscious experience �Res cogitans� (thinking stuff): No physical extension, experience

8. 25/10/2004 PFCS 8 Interactionism Descartes was an interactionist dualist: Animal instincts occur purely reactively, in res extensa The human mind can and does control the higher behaviours of the human body Res cogitans has somehow to become informed about the body and material world, and to somehow control (some behaviours of) the body As is well known, Descartes proposed a seat of interaction in the pineal gland This interaction is the key problem for Cartesian dualism, largely because it has come to seem more and more likely that the physical world is causally closed We certainly otherwise need an account of how and when the mental can cause changes in the physical

9. 25/10/2004 PFCS 9 Parallelism Another form of dualism is parallelism (Malebranche, Liebniz) The separate worlds of the mental and the physical have been set up so that, although they do not causally interact, they operate precisely in parallel On all existing accounts, God has created (or is continually re-creating) the world in this way

10. 25/10/2004 PFCS 10 Epiphenomenalism What if we can account for behaviour purely in terms of causal interactions in the physical world? Then, we seem to have told the whole story about what happens, but seem not to have captured the mental Perhaps appropriate physical events have side-effects in some separate mental realm? Experience cannot cause changes in the physical world, but it is caused by appropriate happenings in the physical world This remains an actively discussed possibility

11. 25/10/2004 PFCS 11 Why Discuss Dualism? Dualism remains important because: No one has successfully explained how all the properties of mind are properties of matter to more than a few people�s satisfaction Dualism is still assumed to be the normal point of view of the �person in the street� The �Cartesian theatre�

12. 25/10/2004 PFCS 12 Behaviourism The end of a long period (> 2000 years) when mental terms were essentially shared by scientists and non-scientists Influenced by logical positivism, behaviourists wanted to explain the mental purely in terms of observables Why insist on behaviour (why not look inside the brain)? Because the average person can use mental terms perfectly well with no theory (or even a wrong theory) of what goes on inside the brain & body Because children can learn how mental terms refer with access to nothing but behaviour

13. 25/10/2004 PFCS 13 Scientific & Philosophical Behaviourism Pure scientific behaviourists (e.g. J.B.Watson) were quite happy to do away with all mental terms (belief, desire, consciousness, experience) as: �heritages of a timid savage past� of a piece with �superstition�, �magic� and �voodoo� Philosophical behaviourists (Carnap, Hempel, Ryle, and scientists including B.F.Skinner) wanted to show that our talk about beliefs, desires, etc. was about nothing more than behaviour

14. 25/10/2004 PFCS 14 Problems with Behaviourism Belief and Desire: In behaviourism, belief and desire don�t explain your behaviour, they are your behaviour � seems counter-intuitive Memory: Is memory really just conditioning history? It seems much more parsimonious to capture how an animal will behave by referring to its internal state now

15. 25/10/2004 PFCS 15 Problems with Behaviourism �Paul has a toothache� (Hempel): Wince Groan Say �I have a toothache� if asked, etc. Have a decayed tooth Have changes in blood pressure Have to disallow 4 & 5 as you can mean that Paul has a toothache without knowing about them Have to disallow 3, Paul has to understand your question, and want to tell you the truth (see next slide) But 1 & 2 don�t capture what you mean by toothache, do they? (Putnam�s objection) Paul could be a super-method actor Paul could be a super-Spartan

16. 25/10/2004 PFCS 16 Problems with Behaviourism �Mary believes it is raining� Mary will get a raincoat, or an umbrella, or stay inside, or say �I believe it is raining� if asked, etc., etc. Only if she wants to stay dry Believes that a raincoat or umbrella will keep her dry Understands what �I believe it is raining� means, and wants to tell the truth It is now widely accepted that you cannot find a redescription of mental terms just in terms of behaviour � to characterise the behaviour correctly, you always end up having to re-introduce mental terms

17. 25/10/2004 PFCS 17 Identity Theory Historically, the next approach was to identify mental states directly with physical states of the nervous system (Smart, Place, Armstrong) The simplest, and oft-quoted, example is to equate pain with the firing of c-fibres C-fibres are a real part of the human peripheral pain system This isn�t meant to be the whole story, but it is meant to be the right sort of story

18. 25/10/2004 PFCS 18 Martian Pain? Few people would deny that states of the central nervous system are relevant to pain in humans But does the firing of c-fibres capture the concept of pain? Could an octopus be in pain? A Martian? If so, then perhaps identifying pain with states of the human nervous system was too fast a move �Species Chauvinism�

19. 25/10/2004 PFCS 19 A Causal Theory of Mental States The central claim of functionalism (developed especially by Lewis & Putnam) is that the essence of a mental state is its causal role In a normal scientific theory, you posit things that you can�t directly observe, but which are interact according to known laws to explain observations: Mass Charge Quarks The Electromagnetic Field Functionalism claims that mental states are the theoretical posits (not directly observable, but in terms of which we explain observations) in our psychological theory

20. 25/10/2004 PFCS 20 The Belief-Desire Theory You have to understand what someone knows, and what they want before you can reason about what they will do If someone believes that food is on the table, and wants to eat, then unless they have any overriding desires or strategies, they will try to eat the food To try to make a functional theory of belief and desire, you have to have as working laws lots of common platitudes: Someone will try to get what they want all other things being equal Someone who wants P, and believes that Q is a means to get P, will try to bring about Q People will generally try to avoid pain People who suffer bodily damage will generally feel pain

21. 25/10/2004 PFCS 21 Pain It is easiest to think about functionalism in terms of a simple state like pain Why should one think that pain has anything to do with causal role? Pain is what causes you to: Groan Wince Withdraw from the painful stimulus We�ve already seen some objections to the notion that pain is the groaning, etc.; but in a functional theory we are allowed to express the reasons why someone might not groan or wince in terms of other countervailing mental states Lewis (following Ramsey) showed that this approach � using non-directly observable theoretical terms � will result in a meaningful theory It may be wrong, but it is not inevitably circular as behaviourist theories are

22. 25/10/2004 PFCS 22 Role and Realiser If we do accept the functionalist story, should we identify the concept pain with the causal role, or with the thing which fills the causal role in any particular instance? The modern debate about functionalism is largely between these two views Authors such as Ned Block and Paul and Patricia Churchland claim that it is the realiser of the mental state which ultimately determines what the state feels like � the feeling of pain in humans will be determined by the physical stuff which fills the causal role in humans A strong functionalist would claim that when you know exactly what causal role pain plays in humans, you could recreate an artificial system in which something else plays the same causal role, and the pain would feel the same (Putnam, all machine functionalists)

23. 25/10/2004 PFCS 23 Levels of Detail NB People who believe that the realiser is more important than the role typically describe themselves as anti-functionalist Modern anti-functionalists accept that there can be high-level descriptions of vision, of hearing, of some aspects of cognition, but claim that you will always have to look at the details to understand how these things works � and what they really are � in each particular instance Functionalism has historically been wedded to the view that you can abstract away from the physical brain/body, to capture everything important about mental life at some higher causal level: Multiple instantiation

24. 25/10/2004 PFCS 24 Physicalism Two main meanings (unfortunately): The same thing as Materialism The aforementioned view that the realiser is more important than the role in capturing the essence of mental states (i.e. the modern anti-functionalist view)

25. 25/10/2004 PFCS 25 Reductionism Reductionism: The Mind can be entirely explained in terms of lower-level sciences (physics, chemistry, neuroscience) Non-reductive materialism: Although there is only physical stuff in the universe, Mind (like economics, art, etc., etc.) exists at a level of description which captures something which cannot be captured at any lower level of description

26. 25/10/2004 PFCS 26 Reading The reading this week is all about looking at the pros and cons of functionalism One thing to consider, are the objections valid just against machine functionalism (the view that we are symbol processing machines), or against conceptual functionalism (identification of pain, belief, etc. with causal roles) more generally? Chinese Room Chinese Nation �Cognition is like digestion�