gentzen

Example of a difficult derivation

6/1/09 [need to check]

4/24/06

Tutorial 25 Exercises h

4/24/06

Tutorial 25 Exercises g

4/24/06

Tutorial 25 Exercises e

12/25/13

Skill to be acquired:

To understand how the various restrictions on the quantificational rules work to exclude certain kinds of invalid inferences

Reading

Bergmann[2004] The Logic Book Section 10.1

The Tutorial

The Rule of Universal Elimination UE

If a derivation contains a line of the form

n (∀<variable>)<scope> <any justification>

then a line of the form

<<scope>[<constant>/<variable>]> 'n ∀E'

Quiz 7 Invalidity

10/30/06 Quiz 7 was formerly known as Quiz 4

Quiz 7 Invalidity

[This has been done in the downloadable application, but the principles apply to the applet version also.]

Quiz 7 Consistency

6/19/09

Quiz 7 Consistent

[This has been done in the downloadable application, but the principles apply to the applet version also.]

Introduction to Semantics

12/25/06

Introduction to Semantics

This video illustrates use of the downloadable application (and the symbol ∧ for 'and'). But, what it depicts and explains is equally good if you happen to be using the web pages applets (or a different symbol for 'and' eg '.').

Replacement or Rewrite Rules

6/21/07

Rewrite Rules

This video uses '&' as the logical symbol for 'and'.

Example of a Harder Propositional Proof: One of De Morgan's Laws

10/23/06

Example