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.
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.
The program, applets, or Notes, should be accompanied by a suitable textbook, such as:
M.Bergmann, J.Moor, J.Nelson, The Logic Book
I.M.Copi and C.Cohen,[2001] Introduction to Logic
A.Hausman, H.Kahane, P.Tidman, Logic and Philosophy
W.Hodges, Logic
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
Most of these pages load java applets and that means that they may take 20 seconds or so to load. [Your browser will then 'cache' the applets and subsequent work will proceed much more quickly.]
The content tailored to the rules, symbols, and stylistic conventions of I.M.Copi and C.Cohen,[2001] Introduction to Logic ISBN-13: 978-0130337351. The content is in the process of being brought into this content management system (with its uniform menus, navigation, tags etc.). The complete content outside the system can be found at http://softoption.us/test/easyDeriver/tutorialsCopi/index.html [The Copi Notes are perhaps more in need of revision than some of the other Notes on this site. If anyone is actively using the Copi Notes, send an email and revising them will be given a higher priority.]
You can try your own derivations below.