gentzen

Tutorial 5: Valid arguments, searching for a proof

Topic
derivations
propositional
Logical System
gentzen

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.

The Tutorial:

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.

We will do a few derivations first, then, in the next Tutorial, explain in more detail what derivations are and how derivations do the work they should.

Tutorial 4: Arguments and searching for a counter example

Topic
propositional
Logical System
gentzen

9/16/12

Skills to be acquired in this tutorial:

To learn how to symbolize arguments, and how to judge whether they might be invalid using truth-table methods.

Why this is useful:

We wish to appraise arguments, to do this we have to symbolize them first. Judging the invalidity of arguments by truth-table methods is not particularly important, but it does help to develop skills involving truth and lists of formulas.

Review

Topic
symbolization
propositional
Logical System
gentzen

There is the idea of setting up a code or convention or dictionary between atomic propositions and capital letters.

There are compound propositions, each of which has a main connective which connects its components.

There are five propositional logical connectives:

'∼' which translates back to 'it is not the case that...'

'∧' which translates back to '... and ...'

'∨' which translates back to '... or ...'

'³' which translates back to 'if... then ...'

'≡' which translates back to '... if and only if ...'

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