Proctor's last speech in Act III is important for a couple of reasons. The first is that it caps off a movement in Proctor's character. From wishing to not be involved and to be isolated, Proctor move into the center of the trials. Proctor is not one who takes this move lightly. Rather, he does as much as possible to not become the center point of the trials. However, his closing speech reveals him to be standing against the trials and defiantly repudiating what the trials have done to Salem. Additionally, Proctor uses his closing speech to Act III to bring to light that the sins he has committed are no different than the sin of the trial, itself. The "blackness" that he alludes to in his speech is reflective of what he sees in the trial and what has existed in his own heart with his adultery. In this, Proctor makes very clear his opinion of the trials and how the concept of "sin" can be relative. The final significance of Proctor's speech is that it firmly sets up the line dividing he and Abigail. If there were any hope in her mind that she could "win" him back, it is removed after his speech. Perhaps, it makes sense that in the next act, Abigail ends up running away from Salem, convinced that she can never obtain Proctor for his price is too high for her.