The title is a play on “To err is human, to forgive divine”. In this book, Petroski discusses a range of engineering failures (e.g., bridge collapses, shuttle disasters, oil well explosions) and explores the physical causes and the larger context in which these designs were allowed to reach their failure point. Sometimes it was a case of not fully understanding phenomena such as metal fatigue (in the case of the Tay Bridge collapse) and other times it’s down to the organizational culture in which profit or timeliness is put before safety (in the case of Deepwater Horizon or Challenger). And sometimes it’s generational: when a revolutionary design is adopted, there is careful documentation and scrutiny, but once it becomes commonplace, the underlying assumptions are taken for granted and the next generation doesn’t always know the challenges that led to the design’s creation. Above all, even though the things engineers create are not human, the engineers themselves and everyone else working on the designs are human, so the designs are a physical embodiment of the assumptions and biases that everyone carries.

This is not a breezy pop-sci book by any means. Pictures are in short supply, and you really have to be interested in the subject matter to carry on. It took me a while to get into it, but I ended up quite liking it. There were some good analogies going on (I had never thought of the parallel between dentistry and engineering), and I found the summaries of the various disasters interesting.

And I learned that the Iron Ring ceremony for engineers is a Canadian thing only, although the United States has developed its own version. The comparison between the two versions, and the discussion of the Canadian version, was really interesting: the Canadian one has more humility, focusing on how you need to avoid repeating the mistakes of the past, and the American version is more gung-ho about all the amazing things engineers can do.

I would recommend this if you like reading about the history of science and technology, are interested in disasters or accident investigation, or if you’re an engineer. ( )