Clojure's dynamic typing is somewhat different from other languages, though, as it really just has two non-atom types: seqs for collections and maps for data objects. Virtually all collections and objects can be manipulated as one of these two types. So "calling a method" on an inappropriate type is basically passing an inappropriate map to a function. You might want to disallow it, but Clojure allows it for good reason: this makes it possible to have many data access/manipulation functions that work on all objects. So the question is, do you want to forbid passing an argument that doesn't make sense to a function or open the door to lots of useful functions that would work on all objects. Clojure simply chose the latter.