The central role of failure in engineering?

[Failures] are object lessons in the history and practice and beauty of engineering. "Failure is central to engineering," [Henry Petroski] said in an interview. "Every single calculation that an engineer makes is a failure calculation. Successful engineering is all about understanding how things break or fail."

From this NYTimes profile of Prof. Henry Petroski, a professor of civil engineering at Duke. The introduction to his new book Success through Failure (Princeton University Press) is here.

Here's an interesting sentence from the article:

For Dr. Petroski, acceptance of uncertainty and possible failure — he calls it "coping with the imponderable" — is what separates the "given world" of the scientist from the "built world" of the engineer.