12/25/06
This video illustrates use of the downloadable application (and the symbol ∧ for 'and'). But, what it depicts and explains is equally good if you happen to be using the web pages applets (or a different symbol for 'and' eg '.').
Your browser does not support html5 video.
To learn how to interpret simple predicate logic formulas as being true or false.
This helps in proving invalidity by the technique of displaying a counter-example.
In propositional logic, we just took it that each of the atomic propositions either is true or is false-- we did not look into the structure of the propositions.
Truth can be discussed in more detail in predicate logic.
A start can be made in predicate logic by taking apart 'atomic' propositions and by re-phrasing what they have to say in a 'entity-has-property' way.
The constant terms a,b,c...h are used to denote entities, the predicates A,B,C...Z are used to denote properties that these entities have, and these are put together by writing the predicate first followed by the term, for example Gb.
There are many valid arguments which cannot be shown to be valid using propositional logic alone. For example,
Beryl is a philosopher.
All philosophers are wise.
Therefore
Beryl is wise.
12/23/05
You now have to tools to appraise propositional arguments.
Let us run through how these might be used with two examples.
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
6/21/07
Rewrite Rules
Your browser does not support html5 video.
This video uses '&' as the logical symbol for 'and'.
-->10/23/06
2/27/06
2/24/06