It seems only yesterday that the fourth edition came out: but — as I found in the CUP bookshop today — there’s now a fifth edition of Computability and Logic. The preface announces that the main revision in this addition is a “simplification of the treatment of the representability of recursive functions”. And the material on Robinson Arithmetic has been rewritten, and there’s a more explicit discussion of the two uses we can make of Church’s Thesis (essential and eliminable).

I confess to still perhaps preferring the more spartan elegance of the early editions. And I think that the book has always been, then and now, rather harder for students than the authors intended (which was one reason that I imagined that there was room for my Gödel book, even though it criss-crosses over quite a bit of the same territory). But credit where a great deal of credit is due: this is still a lovely book, full of good things and with some terrific explanations of tricky stuff. So hasten to your bookshop …

Peter SmithComparing the two tables of contents, the structure seems the same.

BrianI felt very strongly that the death of Boolos and the introduction of Burgess diminished the elegance of it a great deal. Is there any sense that the

structureof the fifth edition is better than the fourth?