Further help with Reductio martin Sat, 12/21/2019 - 11:58
Logical System

Example of a difficult derivation

6/1/09 [need to check]

Fast Start on Web Page presentations (for Instructors)

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
Logical System

Example of a difficult derivation

6/1/09 need to check

Sentential Logic: Try your own derivations

Logical System

Roll your own derivations


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 ∼ & ∨ ⊃ ≡ ∀ ∃ ∴

Review of Sentential Logic admin Sat, 01/11/2014 - 01:50
Logical System

Review of Sentential Logic


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.
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?

Logical System


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

Logical System


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