This was the only point I disagreed with. Is it really so uncommon for programmers to work on code written by others? Yes, it's true that I don't understand programs written by others. To use a debugger, you can get the actual state of the program at the point you want. To use a log, you'll probably have to first understand the program and then instrument it. For fixing bugs in big unfamiliar systems, I think rational ignorance applies. A surgical strike with a debugger will probably be faster.