Yes, but who says it has to be used? In the majority of code, there won't be type checking, but we do want to say something like this:
This function accepts a list of ordinal types
which we can simply put in-code as:
(type-declaration a 'Scanner)
(type-declaration (car a) 'Ordinal)
The point is that the function doesn't specifically accept a list of strings or numbers - it accepts a traversable sequence of anything that can be ordered. The type-declaration thing is just a notation to express that to someone else.
