Do it simply, get it right, then make it fast, in that order.
Lampson's 1983 paper collects hints from real systems rather than deriving principles. The ordering is the argument: correctness after simplicity, speed last, because the reverse order produces systems nobody can fix.
In practice
- A team that ships a correct slow version and profiles it beats one that optimises an architecture that turns out to be wrong.
- A kitchen that gets the dish right before making it fast produces a fast correct dish; the reverse order produces neither.