Henry Petroski

Science is about knowing; engineering is about doing.

The paradox is that when we model future designs on past successes, we are inviting failure down the line; when we take into account past failures and anticipate potential new ways in which failure can occur, we are more likely to produce successful designs.

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.

Many of the familiar little things that we use every day have typically evolved over a period of time to a state of familiarity. They balance form and function, elegance and economy, success and failure in ways that are not only acceptable, but also admirable.

Engineering is achieving function while avoiding failure.

Failure is central to engineering. Every single calculation that an engineer makes is a failure calculation. Successful engineering is all about understanding how things break or fail.

Successful design is not the achievement of perfection but the minimization and accommodation of imperfection.

Any design, whether it's for a ship or an airplane, must be done in anticipation of potential failures.

Everything we do is designed, whether we're producing a magazine, a website, or a bridge. Design is really the creative invention that designs everything.

No design, no matter how common or seemingly insignificant, is without its adamant critics as well as its ardent admirers.

We call the fates of the Titanic and the Concordia - as well as those of the space shuttles Challenger and Columbia - 'accidents.' Foreseeing such undesirable events is what engineers are expected to do. However, design trade-offs leave technological systems open to failings once predicted, but later forgotten.

Case studies of failure should be made a part of the vocabulary of every engineer so that he or she can recall or recite them when something in a new design or design process is suggestive of what went wrong in the case study.

I have always been fascinated by the way things work and how they came to take the form that they did. Writing about these things satisfies my curiosity about the made world while at the same time giving me an opportunity to design a new explanation for the processes that shape it.

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.

It seems to be a law of design that for every advantage introduced through redesign, there is an accompanying unintended disadvantage.

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.

As engineers, we were going to be in a position to change the world - not just study it.

Too much redesign has to do more with fad and fashion than with fitness and function. It is change for the sake of change. Such redesign is not only unnecessary, it is all too often also retrogressive, leading to things that work less effectively than those they were designed to replace.

Failures are much more dramatic than successes, and people like drama. I think this is why automobile races draw such crowds. People expect spectacular crashes, which we tend to find more interesting than cars just racing around the track. The same is true of bridges, buildings, or any structure or machine.