# propositional

Topic
Logical System

## Example of a difficult derivation

6/1/09 [need to check]

Fast Start on Web Page presentations (for Instructors) martin Thu, 10/16/2014 - 17:20
Topic

10/15/14  under construction

[Deriver works in the form either of javascript widgets, which appear directly in a web page viewed through a web browser, or as a downloadable java application, which runs like any other application (usually off the desktop on your computer).]

With the widgets in web pages, it should be fairly clear what the possibilities are. The downloaded application offers more, but at the cost of being more complex.)

Further help with Reductio admin Tue, 01/14/2014 - 14:25
Topic
Logical System

## Example of a difficult derivation

6/1/09 need to check

## Sentential Logic: Try your own derivations

Topic
Logical System

2013

You may have derivations of your own that you wish to try. Just type, paste, or drag and drop, them into the panel, select your derivation, and click 'Start from selection'.

[Often copy-and-paste won't work directly from a Web Page; however, usually drag-and-drop will work!]

You will need to use the correct logical symbols. Here they are

F ∴ F & G ∼ & ∨ ⊃ ≡ ∀ ∃ ∴

Topic
Logical System

## Review of Sentential Logic

2013

You now have to tools to appraise sentential arguments.

Let us run through how these might be used with two examples.

#### Example 1.

Consider the argument

If no human action is free, then no one is responsible for what they do.
If no one is responsible for what they do, no one should be punished.
Therefore
If no human action is free, no one should be punished.

First it should be symbolized

## Supplementary: Why are we doing all these derivations anyway?

Topic
Logical System

3/16/06

So that we can show certain arguments to be valid.

The focus of the course lies with the validity and invalidity of arguments. Now, invalidity can be established by counter-example (by producing an interpretation under which all the premises are true and the conclusion false, at the same time). But validity is a different matter. And the usual approach is to have rules of inference and to do derivations.

## Tutorial 10: Common Inference Patterns and Rewrite Rules

Topic
Logical System

2013

### Skills to be acquired

Becoming familiar with common inference patterns and being able to use them via three new rules of inference and via rewrite rules. This helps with assessing ordinary everyday reasoning such as that found in the law, in newspapers, in advertisements, etc.

Bergmann[2008] The Logic Book Section 5.5

Topic
Logical System

10/23/06

Topic
Logical System

2/27/06

Topic
Logical System

## Or Elimination and Bi-Conditional Introduction

12/23/05

### Or Elimination

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