> > “When you find a problem in the source code, it’s very difficult to explain the consequences of that problem to a judge or jury,” he told me. “It’s written in a foreign language, and the effects are hard to trace. We’re rarely able to say, ‘Aha, here’s this person’s breath test and here’s the problem that caused it to be wrong.’”
This is the true power (and 'problem') of Turing Completeness. The effects of any small change are so absurdly non-linear that it's really hard to predict without systems (types, etc.) to constrain us.
Most non-trivial theorems about TMs are un-provable[0], so this should probably come as no surprise, but I find that it's very hard to explain to lay-people just how hard it is to predict what a program will do.
[0] There are some very important and very general ones that are, but that doesn't really matter wrt. predicability in terms of small changes.