The point is Hickey brings up important points about language design as its experienced by devs actually using the language. Hardly anyone discusses this. Furthermore, you seem to be making my argument for me when you claim that Clojure doesn't have types so why complain about types. In Clojure you could write a type system to do all that, probably in a a dozen hours (the language is programmable after all), but it would be an academic exercise to most which is the point Rich is trying to make when he disparages other type systems.