Computers do not act, they are acted upon

user:  my PDF's aren't working. When I double-click one I just get junk
me:  the filetype association changed...it's trying to open a PDF with MS Word
user:  how did that happen?
me:  it was changed
user:  why did the computer change it?
me:  was there a human involved?
user:  what do you mean by "human"?
me:  ...