# derivations

Topic
Logical System

2/27/06

## Tutorial 9: The Remaining Sentential Rules of Inference

Topic
Logical System

2013

### Skills to be acquired:

Learning the Rules Or Elimination and the Introduction of the Biconditional.

Bergmann[2008] The Logic Book Section 5.1 and 5.4

### The Tutorial:

Or Elimination, in the guise of Dilemma, also is a form of inference dating from antiquity.

Topic
Logical System

2/24/06

## Tutorial 8: Reductio ad Absurdum

Topic
Logical System

2013

### Skills to be acquired:

Learning reductio proof, both as plain Negation Introduction and via (double) Negation Elimination (to prove some formulas that do not have negation as their main connective).

Bergmann[2004] The Logic Book Section 5.1 and 5.4

### The Tutorial:

Reductio ad Absurdum is the second of the classical forms of inference.

## Help with Conditional Proof

Topic
Logical System

9/12/06

### Conditional Proof

This video shows the techniques for Conditional Proof using the downloadable application Deriver. But the techniques are exactly the same for the Proof applet running in a web page. So, the video may look slightly different to what you are looking at, but the underlying principles and approach are the same.

Your browser does not support html5 video.

## Tutorial 7: Conditional Proof

Topic
Logical System

2013

### Skills to be acquired:

Learning conditional proof.

Bergmann[2008] The Logic Book Section 5.1 and 5.4

### The Tutorial:

The five remaining sentential rules of inference are slightly more difficult than the ones that we have met before. They are slightly more difficult in that they require you to make new assumptions, and the correct new assumptions at that. However they follow a similar pattern to each other so mastery of one should lead to mastery of the others.

## Help with Simple Tactics

Topic
Logical System

12/22/05

### Introduction to Tactics

This video is set in the context of the downloadable program, but it applies equally well in the setting of a proof applet.

## Tutorial 6: What is a derivation and what does it prove? How experts do derivations.

Topic
Logical System

2013

### Skills to be acquired in this tutorial:

a) Understanding the nature of derivation. b) Learning elementary Tactics.

### Why this is useful:

Bergmann[2008] The Logic Book Section 5.1 and 5.4.

### The Tutorial:

a)

A derivation or proof consists of a finite list of lines.

Topic
Logical System

Topic
Logical System

## Tutorial 5. Valid arguments, searching for a proof.

2013

### Skills to be acquired in this tutorial:

Proving an argument to be valid by displaying a derivation. Simple propositional derivations using some of the Rules of Inference.