In Predicate Logic there are two new logical connectives, the Universal Quantifier (∀x) and the Existential Quantifier (∃x). These are used for symbolizing certain English constructions (they also have their own rules of inference and their own semantics, which we will learn about later).
8/26/2012
In predicate logic, many different styles of expression in English get cast into the same 'property-is-had-by-entity' form. For example,
8/26/2012
Propositional logic, while good for many purposes, is not adequate for everything. One of the central uses of logic is to judge which arguments are valid and which are not. But 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.
The very first lesson that we have a right to demand that logic shall teach us is, how to make our ideas clear; and a most important one it is, depreciated only by minds who stand in need of it. To know what we think, to be masters of our own meaning, will make a solid foundation for great and weighty thought. [CS Peirce, How to make our ideas clear]
Welcome!
These web pages provide an introduction to logic to the level of Propositional and Predicate Calculus.
The focus of the program is on arguments and the question of whether they are valid. Arguments have the form <list of premises> ∴<conclusion>. An argument is valid if and only if it is not possible for all its premises to be true and its conclusion false at one and the same time; an argument which is not valid is invalid.
To become familiar with the new rules for predicate logic trees.
There are further rules for predicate logic trees (which we will come to shortly).
1/29/08 10Software Under construction
To become familiar with the new rules for predicate logic trees with identity.
It is possible to use trees with formulas containing identity. Two new rules are needed.
2/5/08
2/5/08