All conventional wisdom has an element of truth to it, but good design requires more than an element of truth - it requires an ensemble of correct assumptions and valid calculations.

I employ case studies of failure into my courses, emphasizing that they teach us much more than studies of success. It is not that success stories cannot serve as models of good design or as exemplars of creative engineering. They can do that, but they cannot teach us how close to failure they are.

I emphasize that virtually every engineering calculation is ultimately a failure calculation, because without a failure criterion against which to measure the calculated result, it is a meaningless number.

Henry Petroski Quotes