text and varchar

Why do we have both the type text and type varchar (without limit)?
Couldn't we make one to be an alias for the other?

Since it's 2 distinct types there are some strange effects:

dennis=> SELECT CAST ('123'::varchar AS integer);
ERROR: cannot cast type character varying to integer

dennis=> SELECT CAST ('123'::text AS integer);
int4
------
123

Sure, the cast is simple to fix. But why do we have two types in the first
place?

--
/Dennis Bj�rklund