Why does the tefillin shel yad (hand) have 1 box and the shel rosh (head) have 4 boxes? I know it's because of the physical "structure", i.e. - the yad has 1 parchment and the rosh has 4 separate ...
Why are there four types of execution? Wouldn't it be enough if there were only one type of execution? Lashes for example are only of one type and the standard 40 lashes.