CS486: Applied Logic
Cornell University, Spring 2003


Summary

Logic is concerned with propositions and proofs. A proposition is an abstract mathematical object corresponding to a declarative sentence. We speak of the sense of a proposition, i.e. the thought expressed by it, and of its truth value.
Logic deals with the truth value of propositions independently of subject matter. The raw data of logic are representations of the abstract notion of a proposition. The truth of a proposition depends on its meaning or its sense. Access to truth is via evidence, particularly in the form of proof.
The notion of proof is used also as the basis for meaning; to understand a proposition is to know how to prove it - although one may not know whether a proof can be found. These are the basic concepts of logic and the course presents precise versions of these concepts and the relationships among them.
Computer scientists have shown how to implement the computational core of logics as a programming language and reasoning system combined into one language. Such mathematical systems form a rich class of programming logics which have proven useful in computer science. Conversely, advances in computer science have created a new field of mathematics called Formalized Mathematics. This course will demonstrate these connections between computer science and logic.

CS 486 aims at third or fourth year undergraduates and first year graduate students interested in logic.



Notes from the current course
Lecture 1: What is Logic?
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Part I: The Tableau Method for Propositional Logic
Lecture 2: Propositional formulas
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Lecture 3: Valuations and Truth
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Lecture 4: Analytic Tableaux
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Lecture 5: Consistency
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Lecture 6: Completeness
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Lecture 7: Compactness (Analytic Proofs)
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Lecture 8: Compactness (Lindenbaum's construction)
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Part II: Alternative Proof Methods
Lecture 9: From Analytic Tableaux to Gentzen Systems
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Lecture 10: From Gentzen Systems to Refinement Logic
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Lecture 11: Refinement Logic
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Lecture 12: Correctness and Completeness of Refinement Logic
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Part III: First-Order Logic
Lecture 13: Second Order Propositional Logic (Syntax, Substitution)
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Lecture 14: Second Order Propositional Logic (Semantics and Proof Rules)
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Lecture 15: First-Order Logic (Syntax and Semanctics)
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Lecture 16: First-Order Tableaux (Proof System)
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Lecture 17: First-Order Tableaux (Correctness)
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Lecture 18: First-Order Tableaux (Completeness and Compactness)
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Part IV: Expressing Mathematical Concepts in First-Order Logic
Lecture 19: Functions and Equality
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Lecture 20: Algebraic Structures
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Lecture 21: Axiomatizing Integer Arithmetic
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Lecture 22: Arithmetic Representability
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Lecture 23: Unsolvable Problems in Logic I (Undefinability of truth and arithmetical incompleteness)
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Lecture 24: Unsolvable Problems in Logic II (The theory Q and the undecidability of logic)
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Lecture 25: Lambda-PRL (Formal Language and proof calculus)
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Lecture 26: Proof Automation in Lambda-PRL (Tactics and Decision Procedures)
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