<i>That is close to saying that all languages are equivalent given the same amount of experience.</i><p>Not quite - there are a bunch of languages that are "up there" in terms of expressivity: Lisp, Smalltalk, Haskell, ML, etc. There's no data to say "learning Lisp will give you an enormous productivity boost". There is only data to say "people with 30 years experience in Lisp/Smalltalk/whatever tend to be very good programmers". And, well, duh.<p>Also, if he had to do it in C, say, could he really not? Even if he needed to invoke Greenspun's Law in the process...