My argument is that you can always implement your own breed of type checking either via convention (with appropriate enforcement via static analysis or linting tools if so desired without having to run the code), or you can do type checking at run time -- most dynamic languages have a facility to interrogate a variable to determine its contents and you can implement any number of tests on it as you see fit to validate it.
In practice the difference in guarantees between a static type checking system and a runtime one are so vast that I think they're mostly incomparable. Runtime checking is like doing most of the work of modelling a program with static types but achieving a fraction of the benefit.
