What does The Crucible (play; Arthur Miller) teach us about guilt?

Our group has to do a project on The Crucible and guilt. We've come up with a few things, but can't think of a last one. It has to be a "truth." One of ours' is "It can sometimes cause people to make unintentional mistakes." (as in Elizabeth and Proctor in Act III in the courtroom). Can anyone give me any ideas?