Geoffers,
Just before my son started his course in mechanical engineering, I vividly remember his professor (the head of department at the University) quoting this:
"Engineering is the art of modelling materials we do not wholly understand, into shapes we cannot precisely analyse, so as to withstand forces we cannot properly assess, in such a way that the public has no reason to suspect the extent of our ignorance."
Apparently this was taken from a lecture by a distinguished engineer in 1946. We have made lots of progress since then, but I doubt that the fundamental truth has changed.