INTENTIONAL SYSTEMS:

A. GENERAL SEMANTIC (INTENTIONAL) PHENOMENA.

1. Signs, symbols, names, pictures, icons, schemata, codes, blueprints,...
2. Words, phrases, sentences, expressions, questions,...
3. Representations, information, descriptions, specifications,...
4. Analyses, simulations, accounts, theories, stories, explanations, models,...
5. Pointing, showing, indicating, directing, interpreting,...
6. Languages, communications, discourse, conversations, interactions....
7. Proofs, arguments, demonstrations, rebuttals,...

B. COGNITIVE CORRELATES.

1. Thought, knowldege, recognition, realization, deliberation...
2. Belief, desire, concepts, ideas, decisions, reasons,...
3. Actions, behavior, perceptions, (sensations)....

C. COMPUTATIONAL VERSIONS.

1. Programming languages, specification languages,,...
2. Symbol manipulations, information processing, data analysis,...
3. Databases, knowledge representations systems, meta-level architectures....
4. Programs, instructions, codes, memory, data structures,...
5. Pointers, identifiers, names, variables,...
6. Call-by-value, call-by-name, referential transparency,
7. Syntax, semantics, interpretation, model,...
8. Correctness...

D. THEORETICAL NOTIONS USED TO ANALYZE SEMANTIC PHENOMENA

1. Syntax, semantics, meaning, content, signification, simulation, emulation,.....
2. Reference, interpretation, designation, denotation,...
3. Truth, falsity certainty, likelihood, intension, extension,...
4. Inference, consequence, entailment,...
5. Induction, deduction, abduction,...
6. Logic, consistency, soundness, completeness, validity,..

Characteristics of Intentional Systems

1. Directedness, aboutness: semantics. What about astrology or tarot cards? Intentional or not?
2. Reach, nonlocality in time and place. Noncausality, reference near or far.
3. Separateness, disconnection: dreams, hypothesis, privacy, possibility of error and lies.
4. Aspect, incompleteness. Only certain properties are captured. `representation of X as a Y'. Other characteristics are systematically ignored (eg, are chess pieces wood?)
5. Normative deference: accuracy is an important criterion.

Intentional systems are useful (in natural human intelligence) and artificial versions are equally useful. Classical propositional logic was the original attempt to use (what we would now call) set-theory ideas to explore preservation of normativity (that is, truth preservation) in complex intentional structures.

LOGIC

LOGIC is oldest attempt to capture these properties explicitly - the first artificial intentional system. Can intelligence be understood as formal symbol manipulation?

FORMAL SYMBOL MANIPULATION: basic idea. ``Causal change of state should yield semantically reliable change in interpretation.''

         State-0   --->  State-1
            ||              ||  
            \/              \/ 
         interp-0        interp-1 

``If State-0 is right, then State-1 should be right'' Logic offers basic tools for achieving this.

SIMPLE SENTENCE or PROPOSITION; Eg,

Propositional Calculus.

Sentences (propositions) treated as unanalyzable wholes.

Sentential Operators: AND, OR, NOT, IMPLIES, IFF (Their truth tables!)

Truth Preservation. The truth tables for the sentential operators imply a method for evaluating the truth of complex logical structures (of arbitrary complexity) if the truth values of simple propositions is given.

Propositional Logic.

Expands logic (late 19th C) by distinguishing Terms and Predicates.

Terms (objects, things),
Predicates (verbs, sentence complements) `sentences with holes'
unary - `__ is black, __ sucks,
binary - `__ is same color as__, __ father of __'
ternary - `__ intermediate in age between __ and __', `__gives __ to __'
See Port's handout for examples and more details.

Other Developments inLogic.

See Barwise and Etchemendy article for further development of the formalisms.

Criticisms of Traditional Logic.

NEWELL-SIMON

`Physical Symbol System Hypothesis'

PSS Definition: `intelligence in all its manifestations'

One of the fundamental contributions to knowledge of computer science has been to explain, at a rather basic level, what symbols are.

Laws of Qualitative Structure: Cell doctrine in biology, Plate tectonics in geology, Germ theory of disease, Atomism in chemistry

History of developments toward artificial intelligence:

Formal Logic
Turing Machine and Digital Computer
Stored Program Concept
List Processing - symbols with references (designations)
LISP