Philosophy and Cognitive Science

1. Philosophy and Cognitive Science Conceptual Role Semantics Joe Lau Philosophy HKU

2. Readings • Robert Cummins • Excerpts on reserve at main office. • Ned Block • Online article. • “Advertisement for a theory of semantics”, on reserve.

3. Topic • Some closely related theories • Conceptual role semantics (CRS) • Computational role semantics • Functional role semantics • Procedural semantics

4. Three questions about a representational system • Which are the representations? • What do the representations mean? • What makes a representation mean what it does?

5. Q1 : Identifying representations • Which physical properties / states / objects are used to encode information / carry meaning? • Which are the symbols? • Information encoded by single neuron in the brain, or groups of neurons? In what form? • Structured? Pictorial? Linguistic?

6. Q2 : What do they mean? • Identifying their content / what the symbols represent. • “insalata” means salad in Spanish. • The firing of this neuron represents the boundary of a surface.

7. Q3 : theory of meaning • Questions that remains even after the meaning of a representation is known. • Given that X means Y, what explains the fact that X means Y? • What is it for something to have a particular meaning?

8. Q2 Specifically about a system of representation. An empirical question to be resolved by empirical investigations. Q3 A general question about the nature of meaning. A philosophical question about how the concept of representation is to be understood. Comparing Q2 and Q3

9. CRS • A theory of meaning that proposes an answer to the third question. • Better : a very rough and incomplete framework for answering the third question.

10. Intrinsic vs. relational properties • An intrinsic property of X : a property that depends only on those properties internal to X. • Example : the mass of an object • A relational property of X : a property of X that depends on objects that exist externally of X. • Example : being a father

11. Meaning as a relational property • Being meaningful, having a particular meaning are relational properties of representations. • The intrinsic properties of a physical object is not enough to determine its meaning. • The meaning of a representation can change without changing its intrinsic properties.

12. A unitary theory? • Is there one single theory of meaning that applies to : • meaningful expressions in natural languages • meaningful mental representations

13. Meaning as covariation • The meaning of a mental representation X depends on what X covaries with. • X covaries with Y = X causally correlates with Y

14. Example • Hubel and Wiesel : orientation selectivity in the primary visual cortex (area V1) • Activity of cells represent the presence of bars or boundaries at a certain orientation.

15. Criticism • At best : works for “detector” representations that indicate proximate stimulus. • Still : such representations might covary with lots of things. • But not the higher cognitive representations. • Inaccurate covariation • Non-existent covariation

16. Functional role semantics • Functionalism : Mental states are defined by their functional role. • Role vs. occupant • Intentional mental states are defined by (a) type (e.g. belief) and (b) content (e.g. that snow is white) • So the content of intentional mental states are defined and explained by their functional role.

17. Functional role = ??? • A relational property; role within the functional organization of the mind • Conceptual role semantics (CRS) • Content defined by the role of a representation in cognition, e.g. reasoning, decision, perception, memory.

18. Example • Consider these inferential transitions between the beliefs of an agent : • P*Q P • P*Q Q • P, Q  P*Q • Interpretation : “*” represents conjunction (“and”). • Meaning determined by role in reasoning.

19. Advantages of CRS • Explain differences in meaning despite sameness of reference. • Lee : “I have a lot of money.” • Lee : “Lee has a lot of money.”

20. Computational-RS • CompRS = CRS + Computationalism • Computionalism : cognition is explained by computations. • Mental content defined by conceptual role  Mental content defined by computational role (role of representation in the mind’s program)

21. CRS and FRS • CRS is one version of FRS • CRS is true  FRS is true • FRS is true not  FRS is true • There might be aspects of functional role which are not computational. • e.g. role in interacting with some non-computational system.

22. CRS and covariation • Internal conceptual role might not determine all aspects of meaning. • External causal connections have a role in determining which particular object a representation is about. Tung-1 Tung-2

23. Two factor CRS • Which is more important? Internal or external factor • Is this plausible? • Internal factor imposes constraints on what the representation can be about • External factor determines which particular object or property is represented. • But perhaps some content is determined entirely by the internal factor (e.g. “and”).

24. Narrow vs. wide content • Narrow content : content that depends only on what is inside the head. • Wide content : content that depends also on objects outside the head.