Writing program code is a good way of debugging your thinking.
-- Bill Venables
That seems like the extreme case of "you don't really understand something until you can explain it to somebody else", which I'm sure somebody other than me must have said a long time ago.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.