I'd say it is an engineering truism, gleaned from experience with designing and building physical things, that has been adopted by the software community. The

I'd say it is an engineering truism, gleaned from experience with designing and building physical things, that has been adopted by the software community. The way I originally heard it was that problems are 1 x harder to fix during design, 10x harder during prototype and 100x during production. It's about orders of magnitude rather than the numbers. Another way of putting it is: problems get harder to fix the later you detect them.