New Computationalism
Ron ChrisleyCOGSDepartment of InformaticsUniversity of Sussex
School of Humanities and Information, University of SkövdeOctober 19th, 2006
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Overview
Will discuss four related claims/ideas:1. "Transparent" defense of
computationalism2. Falsity of the Church-Turing thesis3. Falsity of pan-computationalism4. Even if computationalism is false,
strong AI is possible
Transparent computationalism
• The claim that cognition is computation can be construed opaquely or transparently
• Opaque construal: The mind is best understood in terms of the concepts from current (or past!) computational theory
• Transparent construal: The mind is best understood in terms of whatever concepts, it turns out, best explain what computers do
• Many critiques of computationalism succeed only on the opaque construal
• Thus, transparent computationalism is not threatened
The transparent strategy
• For each critique, present:– A current (opaque) view of
computation– The critique based on that view– An alternative view of computation
that avoids the criticism– Independent motivation for that view
of computation
Critique 1: Dynamics
• Opaque view: Discrete steps in an algorithm essential to computation
• van Gelder:– Cognition isn't discrete, but
fundamentally dynamical– Therefore, cognition isn't computation
Dynamical computation
• Alternative view: Generalise notion of an effective procedure to include any physically realisable and exploitable process, even dynamical ones
• Independent motivation:Real-time computational control of an airplane wing
Critique 2: Externalism
• Opaque view: Computational properties are syntactic and local
• Fodor:– Psychological properties are semantic
and relational/external/non-local– Therefore, there can't be a
computational psychology
Externalist computation
• Alternative view: Even computational explanations are external/relational (cf Peacocke's "Content, computation and externalism", 1994)
• Independent motivation: Embedded computational systems
Critique 3: The Chinese Room
• Opaque view:1. All essential computational properties are
formal2. Non-formal properties of a computation are
mere implementation detail
• Searle:– Formal properties are insufficient for mind– Therefore, there can't be a computational
psychology
Grounded computation
• Alternative view:1. Having a semantics is crucial to
computation 2. Some properties that current formal theory
takes to be irrelevant play a constitutive role in determining computational state
• Independent motivation:1. Not every process is a computation2. Real-time computational control of an
airplane wing
The Church-Turing thesis
• An example of an explicit acknowledgment of the distinction and relation between informal and formal (theoretical and pre- theoretical) notions
• Diagonal arguments (Gödel, Lucas, Penrose) do not show what they purport to: falsity of Strong or even weak AI
The Church-Turing thesis
• Diagonal arguments highlight a special case of a general property:– For any set of things that can answer
questions, one can construct a question that no member of that set can answer, even though some things outside the set can.
• Implies, e.g., that odd-numbered TMs can compute functions that even-numbered TMs cannot
• And that TMs can compute functions we cannot
Universality
• One might think this violates Turing's famous result, that there exist universal machines
• But no conflict, since Turing's universality result is about simulation, not computation
Against pan-computationalism
• Putnam's sense: Everything instantiates every computation– fails because of the causal aspect of
causation (cf, e.g., Chalmers 1994, Chrisley 1994)
• More plausible sense: Everything has some computational desciption– Yes, but still too broad: IBM vs BMW– Suggests that we need to do more work to
capture real computation: Semantics
Computation and mind
• Traditionally, two ways computation is relevant to understanding or replicating mind:
1. Weak AI: Computational simulation of mind
2. Strong AI: Cognition is computation
Strong AI without Computationalism
• Even if cognition is not computation, does not imply falsity of strong AI– Not because of pan-computationalism– Third way: computation as the ultimate
plastic– Computation is a convenient way to
configure a system's causal/dynamical profile
– In between identity and mere simulation
Strong AI without Computationalism
• E.g. Suppose life is crucial for mind; and (e.g.) Boden is right that life is non-functional – Does not imply that one cannot
program a system to be alive – Falsity of (even transparent)
computationalism does not imply Strong AI is impossible
Thank you!
Video, audio and PowerPoint files of this talk and others can be found at:http://e-asterisk.blogspot.com
Comments welcome: [email protected]