IFL2: Propositional truth trees

My favourite new encounter from among my recent late-night reading has been with Jane Gardam’s 1985 novel Crusoe’s Daughter. 

Its metaphorically cast away heroine Polly Flint is talking of novels (she is devoted to Defoe) when she remarks “Form is determined by hard secret work — in a notebook and in the subconscious and in the head.” What applies to writing novels applies to logic books too — including the bit about the subconscious. Even when your head says that the notebook drafts of some section is fine, your subconscious can remained troubled, unable to settle and remain content with what you’ve written. And then, from somewhere — without it seems conscious reflection — you are struck by how to resolve the nagging worries, and can move on.

Anyway, whatever the processes involved, I have been re-revising the revisions of the chapters on propositional trees in An Introduction to Formal Logic. (Ignore my recent wobbles about whether to drop trees in the new edition — my subconscious just couldn’t rest hppily with that!) So, after an introductory Interlude, there are now three short chapters, significantly shorter than the four chapters. But I think the result is still a very clear introduction to the truth-tree method.

I should add that tree-rules for biconditionals and examples with biconditionals are a topic for the end-of-chapter Exercises (not in this version).

All comments and/or corrections (either here or to the email address in the watermarked header) are as always most welcome.

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