Link: Code Only Says What it Does
Marc Booker's Code Only Says What it Does (via) is about what code doesn't say and why all of those things matter. Because I want you to read the article, I'm going to quote all of the first paragraph:
Code says what it does. That's important for the computer, because code is the way that we ask the computer to do something. It's OK for humans, as long as we never have to modify or debug the code. As soon as we do, we have a problem. Fundamentally, debugging is an exercise in changing what a program does to match what it should do. It requires us to know what a program should do, which isn't captured in the code. Sometimes that's easy: What it does is crash, what it should do is not crash. Outside those trivial cases, discovering intent is harder.
This is not an issue that's exclusive to programming, as I've written about in Configuration management is not documentation, at least not of intentions (procedures and checklists and runbooks aren't documentation either). In computing we love to not write documentation, but not writing down our intentions in some form is just piling up future problems.