Sermon: The Law (Why A Savior series)

Why did God have to send a savior to save us from our sins?  After all, if he's all-powerful, couldn't he just snap his fingers and make "grace" happen?  There is a reason for the Messiah and understanding that reason starts with understand why this thing called "The Law" exists.  "The law" is often considered nothing more than an archaic set of rules and rituals for the Hebrew people, but was there something more to it?  If it was just mere "actions", then why does Christ seem to criticize the Pharisees for doing all the "right actions"?  There must be something more to "the law" than just what we think of as human laws and understanding it's purpose is the beginning to helping us understand why we were sent a Savior.