What point does Priestly make about guilt in this play?

The point Priestly is making in 'An Inspector Calls,' is that everyone in society has a collective responsibility to take care of each other. And that when a tragedy (like Eva's death) occurs; we all share in the blame because we're to take care of the people around us. The Inspector tells the family, "each of you helped to kill her." But in the Inspector's final moments on stage, he directs his speech not only at the family gathered around him but the audience as well.