What is the importance of John Proctors last speech in Act III?

I love this speech. John has a chance to save himself and his beloved wife Elizabeth. Instead he rips up his confession (which is a lie) and screams he can't confess in writing because, "All I have is my name!" This goes to the heart of the Crucible. At the end of the day truth is truth. After his adultery and all the hysteria John realizes that if he is not true to himself then he amounts to nothing.