UPDATE—11 March 2009
Jape now works on Tiger (Apple's Mac OS X 10.4). Dr. Bornat sent me a new version compiled by his collaborator, Bernard Sufrin, and it worked fine. I assume jape.org.uk will soon add this version for download.


Although I've had some difficulty installing Jape on my Mac (perhaps because I'm a Tiger hold-out) I've started to use it using a Linux emulator. The screenshot shows a proof in progress using natural deduction. (You may click on the image for a full-size view.)

I became interested in Jape (jape.org.uk) while reading Richard Bornat's Proof and Disproof in Formal Logic: An introduction for programmers (Oxford University Press). (My own personal interest is more directed to proofs in philosophical terms than programming, I should note.) Describing his proof software forms a major part of the book. He writes:

Jape is a calculator. It deals with logic in the same sort of way that arithmetic calculators deal with numbers: you choose a button and press it; Jape makes the corresponding calculation step and shows you the result, but it doesn’t give any advice about choosing steps or criticism about the step you chose. By trying out steps and then undoing if they don’t work, you can use Jape to search for logical proof. Once you get good at search, you will find that you have learnt a proof strategy — a way of tackling problems that more or less guarantees success — and you can transfer that strategy to blackboard-and-chalk or pencil-and-paper or musing-on-the-bus proofs. (vi–vii)

How to Use Jape

Two introductions to Jape are the guide to using Jape with natural deduction (PDF from the Manuals section of the Jape home page), and his 2005 book, Proof and Disproof in Formal Logic: An introduction for programmers (Oxford University Press).

I've also gathered together some of my own notes into an article entitled (unsurprisingly) Jape Notes.

Installation Issues

Jape wouldn't work on my Intel MacBook Pro (vintage ca. 2006) running Tiger (not its Leopard successor). It's not a critical issue for me as I can run it on Linux using the VirtualBox emulator. See Jape Installation from a more free-ranging wiki of mine for more details.

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