"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." – Brian W. Kernighan
It's such a great line, and such a classic one, that you don't even notice that the premise isn't true. It's like the opening line to Anna Karenina in this respect.
Do you mean that debugging is infinitely harder than writing the code in the first place (since you can never verify correctness) or that debugging isn't more difficult? In the former case, while it is factually incorrect, in the general sense it's true.
Debugging is not always harder than writing the code in the first place (let alone "twice as hard" - what does that even mean)?
Debugging doesn't mean proving there are no bugs. If it did, the quote would be even more wrong, since our inability to do that has nothing to do with how cleverly code is written. But that's beside the point, since nobody uses "debugging" to mean this; it means tracking down and fixing bugs you know about. And it's trivial to see that that's not always harder than writing the code in the first place: some bug fixes (e.g. typos) are easy.
I guess I'm taking it for granted that any piece of code is going to have multiple bugs in it, and you're going to spend more time debugging than you did writing. I still don't think you've said anything that shows the maxim to be false in the general sense, only in the sense that it could be worded a little more clearly.
