Copi, Symbolic Logic, 5th Ed.
There is no solutions manual for Copi's Symbolic Logic. Peter Suber made his own solutions available some time ago, but they don’t go deep enough into the book for many of us. This semester I had a fantastic student in Symbolic Logic—Jon Ross—who undertook to continue Suber's work. I am pleased to present Jon’s solutions—they will perform a very useful public service. Thanks Jon!
University of Missouri–Kansas City
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First of all, Peter Suber began this project many years ago, but didn't get around to finishing it. <http://www.earlham.edu/ ~peters/courses/log/loghome.htm> After working through Copi's text and checking my results against Suber's solutions along the way, I felt that it would be worth my time to complete what he started. So I took up where he left off, with a few slight modifications from his 'style' of proving arguments. I prefer Copi's (classical) notation over the prenex normal form, simply because I find it easier to bounce back and forth between the English version and its symbolized counterpart. Admittedly, it is slightly more cumbersome to manipulate the classical notation in formal proofs. But in my mind, none of the arguments up to this point in the text are complex enough to warrant the use of the more powerful, albeit less intuitive format. The only other difference between Suber's proofs and my own lies in my refusal to resort to an indirect proof, regardless of whether it makes the proof drastically simpler or not. Again, this is a personal preference, based on some metaphysical beliefs. Since anything can "fall-out" of a contradiction, I just avoid them completely. I tend to side with the constructive mathematicians and the intuitionistic logicians who require "constructive proofs." That is, anytime an existence claim is being made, there should be a way to "construct" it from the premises, not simply claiming that it follows from the fact that a contradiction arises. I hope these solutions (chapter 5, chapter 7, and Chapter 8) prove useful. I plan on adding to the set of solutions as I make my way further into the text. If you discover any errors or need any clarification on anything please feel free to email me at: email@example.com.
(The problems all come out of Irving Copi's Symbolic Logic, Fifth Edition, Macmillan, 1979)