Logical Foundations of Cognitive Science

Transcription

1 Logical Foundations of Cognitive Science Harold Boley NRC-IIT Fredericton Faculty of Computer Science University of New Brunswick Canada Institute of Computer Technology, TU Vienna Winter Semester 2008/09 Adapted from a course by Kelly Inglis on Philosophy and Cognitive Science, Philosophy Dept., University of Hong Kong,

2 Optional Readings No course textbook. Some readings are available online. Readings for today: 1) They re made of meat by Terry Bisson home.earthlink.net/~paulrack/id82.html 2) What s philosophy got to do with it? by Tim van Gelder

3 Topics for today What is cognitive science? What is the role of philosophy and logic in cognitive science? The mind-body problem

4 What is Cognitive Science? Cognitive science is the scientific study of the mind. How does the mind work? How does the brain produce intelligence?

5 Cognitive science is an on-going project Started in 1950s The term cognitive science was coined in 1973 Still at early stage of development

6 Cognitive science is a science A central principle is that the mind can be understood scientifically A materialist approach

7 Cognitive science is interdisciplinary Draws on: psychology neuroscience computer science anthropology linguistics philosophy logic

8 The six blind men and the elephant We are the blind men. The mind is the elephant.

9 Contributions of different disciplines: Psychology and Linguistics: study human behavior, how people act, how people talk, what people say about their own mental experiences. Learn the output of the mind. Anthropology: Learn how the brain evolved. Learn how thinking differs in different cultures. Learn what thinking processes remain the same in all cultures.

10 Neuroscience: study the brain directly. See how the brain is organized, see the brain in action (on MRI scans), experiment on animal brains, study effects of brain damage. Philosophy and Logic: Putting it all together Formalizing theories about it Computer Science: Model functions of the brain in computer programs. Learn how the brain might accomplish these functions. Visualize (e.g. Grailog), mechanize, and implement logics

11 Themes of cognitive science What are mental states? How do they correspond to brain states? How do mental representations acquire meaning? Are many of our concepts and mental abilities innate, or are they all acquired through experience? Is human thought conducted through a language-like code (possibly innate) such as can be modeled in a traditional computer program, or is thinking conducted through a connectionist neural-network architecture?

12 Themes of cognitive science (cont.) Is folk psychology an accurate reflection of what is going on in our heads? Or is it a highly-distorted simplification? What is consciousness? What is the function of consciousness? What is the relation between unconscious brain activities and conscious mental functions? Do we have free will? Or are all our actions merely results of the mechanical operation of physical laws?

13 The Role of Philosophy and Logic in Cognitive Science Philosophy and Logic are sometimes dismissed as obscure, meaningless and trivial. How can such abstract unworldly disciplines contribute to a serious scientific quest to understand the mind? What we will do? Analysis Conceptual clarification Asking questions Model (and criticize and improve) our theories

14 What do philosophers and logicians do for cognitive science? Analyze and evaluate the arguments of others, often showing up flaws in another cognitive scientist s reasoning Clear up conceptual confusions, often showing that different researchers have different meanings in mind when using the same word (e.g. consciousness). Ask questions, often pointing researchers towards new directions Propose theories that are not (yet) empirically sound, often spurring researchers to do the empirical studies that can prove them right or wrong.

15 In What s philosophy got to do with it?, Tim van Gelder lists several roles a philosopher can play in regards to cognitive science: 1) The Pioneer Historically: Science started as philosophy Materialism, the basis for cognitive science Philosophy of mind, the original cognitive science Many specific cognitive science theories invented first by philosophers: thought is a form of symbolic computation there is a language of thought the mind is modular

16 1) The Pioneer (cont.) Currently: The nature of consciousness How the brain creates meaning Do we have free will? 2) The Building Inspector Questioning the foundations of scientific enquiry. Are the assumptions well-grounded? Are there other, asyet-unimagined ways for things to be? E.g. theory of relativity

17 3) The Zen Monk Provides society with the assurance that someone is thinking about deep, important problems (such as the meaning of life), even though the results of this deep thought may have no practical benefits to anyone. 4) The Cartographer The philosopher is able to peruse data and theories from the various interconnected disciplines of cognitive science and help put it all together, drawing up a map of what we understand of the mind and how it relates together, and also placing the current state of knowledge in a historical context.

18 5) The Dilettante Knowing something, but necessarily not everything, from all of the different disciplines and perspectives available. 6) The Archivist Following the progress of different disciplines from a broad historical perspective.

19 The Cheerleader Seeking out significant theories and lines of research and bestowing official philosophical approval on them, thus bolstering certain fledging new approaches to modeling or understand the mind. The Gadfly Promoting startling new theories or attacking established ideas in order to stir up debate and spur cognitive scientists on to either defend their own theories or consider new possibilities.

20 The Mind-Body Problem How can the brain think? Two possibilities: 1) Dualism 2) Materialism

21 Dualism Two types of stuff or properties of stuff: physical and mental Kinds of dualism: 1) Substance dualism Descartes: I am a thinking thing 2 kinds of stuff: physical stuff and mind/soul stuff Mind stuff: immaterial, no physical properties, not detectable by physical means

22 Kinds of dualism (cont.) 2) Property dualism There is one kind of stuff, but some stuff has two kinds of properties: mental properties and physical properties. Mental properties are undetectable by science and do not follow physical laws

23 Problems with dualism What is non-physical stuff? How does mind stuff interact with physical stuff? The physical affects the mental; does the mental affect the physical?

24 Problems with dualism (cont.) The physical world is causally closed (conservation of energy) The problem of epiphenomenalism Ockham s razor. Why posit mind stuff? Mind stuff adds nothing to an explanation of the mind

25 Materialism Everything is physical. The mind is composed of atoms, particles and forces. We are composed of stardust. The only difference is organization.

26 Kinds of materialism 1) Identity theory: every mental state is identical to a particular physical state A problem with identity theory: alien minds 2) Supervenience: The mental depends on the physical but it is not identical. If two people are identical in their physical properties, they must also be identical in their mental properties. But not vice versa.

27 Kinds of materialism (cont.) 3) Functionalism Mental states are defined by their functional roles Functional roles relating to behavior and relating to other mental states Multiple realizability Example: a chair, addition, pain Problems with functionalism: Qualia Liberalism

28 The Mind-Mind Problem What is the relationship between the computational mind and the phenomenal mind? Computational mind: intelligence Phenomenal mind: experience

29 Grailog: Graph inscribed logic Course employs Grailog for providing graph visualizations of cognitive and metacognitive content in logic Examples will introduce Grailog as we go One class will be devoted specifically to Grailog:

30 Optional Readings for next week Focus: Extra: Searle, John. R. (1980). Minds, brains, and programs. In Behavioral and Brain Sciences 3 (3), , available at: Hofstadter, Douglas (1981), Reflections (on Minds, Brains and Programs, in Hofstadter & Dennett, The Mind s I (1981), Sober, Elliott, Putting the Function Back into Functionalism, in Mind and Cognition, pgs Block, Ned, Troubles with Functionalism (excerpt), in Mind and Cognition, pgs