NOrman's statement that a native speaker "literally spends a life-time
learning his language" (rough quote) might be misunderstood in
the context of the discussion on whether or not a highly inflected
verb system (like Italian or Russian) is harder for native speakers
to acquire than a minimally inflected one like English. Language
acquistion studies show that Russian children, for example, master their verb
system within the first years of life, effortlessly, just as
English speaking children master theirs. It doesn't take a life-time.
 
The English verb system has its own complexities. Things that are\
expressed through tense in inflected languages must be expresed
through auxiliary verbs (model-have-be) and adverbs in English. Try teaching
the many subtle connotations of models to a foreigner, and you'll
see what I mean. What, for example, are the different degrees of
certainty expressed by these verb phrases:
        He may be upstairs.
        He'll be upstairs.
        He might be upstairs.
        He should be upstairs.
        He has to be upstairs.
        He could be upstairs.
        He would be upstairs.
        He ought to be upstairs.
 
--Bill Murdick