The Annotated Turing by Charles Petzold

The Annotated Turing is a book by Charles Petzold, which I picked up a few years back when I was going through a theory class and wanted some extracurricular reading. As with many attempted extracurriculars, this did not happen that semester, nor the next, nor at all during my education. As the book had finished its proper incubation period last week, I finally read it. I’ve collected some thoughts on it here.

The format of The Annotated Turing is excellent. As the reader, you are taken on a journey through the academic prequels to Turing’s paper and are given a respect and understanding of his mathematical period and mindset. Simultaneously, biographical expositions and characterizations are given for the supporting characters including, but not limited to, Alonzo Church, Kurt Gödel, John von Neumann, David Hilbert, Georg Cantor, Bertrand Russell, Martin Davis, and Stephen Kleene. Comingled with this academic soap opera is an explanation and walkthrough of the highly technical Turing paper itself, and a much more detailed biography of Alan Turing himself. This structure leads to the reader emphatically celebrating accomplishment as Turing’s paper flourishes with mathematical climaxes and his contemporaries push him up to the highest echelons of the academic establishment. Likewise, as the world is going through the second world war and Turing himself is being prosecuted afterwards in England, the reader is imbued with an appreciation for just how grave the damage to human progress was when Turing’s life was stifled by the British government’s homophobia.

As the reader, I already had a lot of context about Turing’s paper, having studied it, its predecessors, and its successors ($$S(Turing)$$) previously. Because of this, I had no trouble understanding the walkthrough of Turing’s On Computable Numbers. That being said, I believe this book provides adequate exposition such that a mathematically curious, but not necessarily experienced, mind would be able to understand and enjoy it as well.

Even having a preexisting understanding of Turing’s paper, Petzold offered further insights and context into the details that I would never have considered or known about. So, my experience most certainly was not so vast as to preempt the technical content of this book.

The non-technical parts of this book were, however, what I enjoyed the most. My attraction to this particular part of Computer Science, the part which intersects with Philosophy, Linguistics, Mathematics, and Logic, is fueled only partly by genuine interest in the content. The remainder of the fuel is interest in the incredible personalities, amazing thinkers, and generally dramatic people that this area of thought attracts. I have always read the names, which I enumerated above as the supporting characters, in papers and textbooks and imagined them all to be the essential prototypical stuffy academic. To be introduced to their place in the world, their lives, slivers of their personalities, their humanity, was a beautiful and thrilling thing.

Turing’s contributions to mathematics were appreciated during his lifetime, which is some consolation. But he never could have known just how hallowed his name would become. Rarely can we, by ourselves, usher on the dawn of a new era or gift progress to humanity. Much more ascertainable is to contribute to the effort. Turing contributed his great mind, and it unlocked the final piece in a puzzle that mankind had spent thousands of years pondering. With this puzzle behind us, a new frontier was exposed. As Benjamin Zander said in one of his published “Interpretation Classes”:

Life isn’t about progress. It is about contribution.