# gentzen

Topic
Logical System

## Example of a difficult derivation

6/1/09 [need to check]

Help with Tutorial 25h admin Sat, 01/11/2014 - 01:50
Topic
Logical System

4/24/06

### Tutorial 25 Exercises h

Help with Tutorial 25g admin Sat, 01/11/2014 - 01:50
Topic
Logical System

4/24/06

### Tutorial 25 Exercises g

Help with Tutorial 25e admin Sat, 01/11/2014 - 01:50
Topic
Logical System

4/24/06

### Tutorial 25 Exercises e

Tutorial 24: The restrictions on the quantificational rules admin Sat, 01/11/2014 - 01:50
Topic
Logical System

### Skill to be acquired:

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

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

Logical System

## 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.]

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Logical System

## 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.]

Help with Introductory Semantics admin Sat, 01/11/2014 - 01:50
Topic
Logical System

## 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 '.').

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Topic
Logical System

## Replacement or Rewrite Rules

6/21/07

Rewrite Rules

Another Example of a Harder Sentential Proof: One of De Morgan's Laws admin Sat, 01/11/2014 - 01:50
Topic
Logical System

10/23/06