Physical Symbol System• INTRODUCTION• HYPOTHESIS

Submitted by :Nida Quazi

Contents

Physical symbol system (introduction) Statement Basic idea Philosophical roots Examples of PSS Contribution of Newell & Simon Attacks on P.S.S.

Physical Symbol System

Also known as Formal system. It Physical Patterns

(Symbols)

Structures(Expressions)

New Expression

Hypothesis

This hypothesis has a great position in philosophy of Artificial Intelligence.

Formulated by - Allen Newell & Herbert A. Simon .

They proposed that "symbol manipulation" is the essence of both human and machine intelligence ; which mean that human thinking is symbol processing.

“

”A physical symbol system has the necessary and sufficient means of

general intelligent action .

Statement of Hypothesis

“Symbolic behavior of man arises because he has the characteristics of a physical symbol system .”

This is a very strong claim as it implies both that :human thinking is a kind of symbol manipulation (because a symbol system is necessary for intelligence)andmachines can be intelligent (because a symbol system is sufficient for intelligence) .

Basic idea

Symbol are physical patterns. Symbols can be combined to form complex symbol

structures. The system contains processes for manipulating complex

symbol structures. The process for representing complex symbol structures can

themselves be symbolically represented within the system.

Philosophical roots

Idea has roots in:1. Hobbes : claimed reasoning is "nothing more than reckoning".2. Leibniz : attempted to create a logical calculus of all human

ideas.3. Hume : thought perception could be reduced to atomic impressions.4. Kant : analyzed all experience as controlled by formal rules. Latest version is called computational theory of mind - Hillary

Putnam & Jerry Fodor.

Examples of PSS

Formal logic or Algebra

Digital computer

Chess

SHAKEY ROBOT

NAVLAB

STANLEY

Appropriate & less appropriate

Hypothesis is a core part of A.I. : Appropriate for higher level intelligence such as chess playing but less appropriate for commonplace intelligence such as vision.

Contribution of Newell & Simon

Contributed in :1. Information processing language (1956)2. Two of the earlies A.I. program : I. Logic Theory Machine (1956) II. General Problem Solver(1957) They were awarded ACM's A.M. Turing Award in 1957.

I. Logic Theorist

A computer program written in 1955-56 ; called the first A.I. program.

By Newell, Simon & Cliff Shaw(computer programmer). First computer program to mimic problem solving skills of a

human being. Eventually prove 38 of the first 52 theorems, chapter 2,

Whitehead & Russell's Principia Mathematica and found new and more elegant proofs for some.

L.T.'s influence on A.I.

L .T. introduced several concepts that would be central to A.I. research such as :

1. Reasoning as search 2. Heuristics3. List processing

II. General Problem Solver

Computer program created in 1957. Was intended to work as universal problem solver. It was the first computer program which separated its

Knowledge of problem (rules represented as input data) from its strategy of how to solve problem (a generic solver engine).

G.P.S. focus on the available operations, finding what input were acceptable and what output were generated. It starts with symbolic descriptions of the start state and the goal state.

It then creates subgoals to get closer and closer to the goals, i.e. aims to find a sequence of admissible transformations that will transform the state into the goal state.

Applicability of G.P.S.

1. Proofs in predicate logic2. Euclidean geometry problems

Attacks on P.S.S.

1. Focuses on the presumption that computers can only manipulate meaningless symbols.

2. Focuses on presumption that much that underlies intelligent action, especially perception, involves non symbolic processing.

3. Claim that “computation” as it is ordinarily understood , does not provide an appropriate model for intelligence.

4. Based on observation that much that appears to be intelligent behavior is really “mindless”.

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