## Example of a Harder Sentential Proof

## Example of a Harder Propositional Proof

2/27/06

Topic

Logical System

2/27/06

Topic

Logical System

2013

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

Bergmann[2008] The Logic Book Section 5.1 and 5.4

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

Topic

Logical System

2/24/06

Topic

Logical System

2013

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

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

Topic

Logical System

9/12/06

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.

Topic

Logical System

2013

Learning conditional proof.

Bergmann[2008] The Logic Book Section 5.1 and 5.4

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.

Topic

Logical System

12/22/05

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

Topic

Logical System

2013

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

Tactics will help you to do derivations.

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

a)

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

Topic

Logical System

Topic

Logical System

2013

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

Bergmann[2004] *The Logic Book Section 5.1*.

If you suspect that an symbolized argument might be valid, you should attempt to give a derivation of it.

A derivation is a proof of validity.