Not buildings, not bridges, not cars, not airplanes, not software. There are mistakes in every field of engineering and the best we can hope for is to minimize them as much as possible.

Engineering is knowing (among other things) how to categorize the potential mistakes, develop procedures to reduce the chance of them being made and in the case that some slip through (and they will), estimate their impact and decide when you're "good enough."

Software engineering is no different.