The English words were spelled phonetically at the time the spellings were determined. That is to say, those silent 'e's at the end of a word were pronounced; and a word like "knight" was actually spoken with a k-sound, the gh as a guttural sound. The spoken language changed but the printed remained relatively stable, so now our words have some incredibly strange spellings. Think cough, hiccough, plough, though, tough, through. I'd hate to have to learn English as an adult...

Update: corrected minor spelling error.