Easy Deriver [Propositional and Predicate Logic—Gentzen Syntax]
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.
An argument can be proved to be invalid by displaying a scenario (truth table, a possible world, an interpretation ...) under which all its premises are true and its conclusion false. EasyDeriver has the tools to allow you to do this.
An argument can be proved to be valid by displaying a suitable derivation or proof of it, and EasyDeriver's also has the tools to do this.
These web pages, or Notes, should be accompanied by a suitable textbook, such as:
M.Bergmann, J.Moor, J.Nelson, The Logic Book
A.Hausman, H.Kahane, P.Tidman, Logic and Philosophy
C.Howson, Logic with Trees
R.C.Jeffrey, Formal Logic: Its Scope and Limits
H.Leblanc and W.Wisdom, Deductive Logic
B.Mates, Elementary Logic
M.D.Resnick, Elementary Logic
Unfortunately these textbooks use slightly different choices of rules and symbols one from another. To adjust to this the Notes are in different major sections, with the sections tailored to particular texts.
You are invited to review