One reality that is evident in the drama is that little in life is certain. Shanley proves that the drama embodies its title. There is only doubt and ambiguity present. Even the absolute certainty of Sister Aloysius is riddled upon the drama's conclusion: "I have doubts! I have such doubts!" There is only ambiguity and uncertainty present. In a condition where there is so much in way of accusations and claims of certainty, Shanley's drama leaves only doubt present.
In this construction, the end lesson is that one cannot avoid the condition of uncertainty that plagues the modern setting. This is not one in which action should not be taken, as it becomes clear in the drama that not taking action is almost as bad as anything else. Yet, it is one in which individuals cannot claim to hold an absolute and dogmatic view of the truth. There is intricacy and complexity present in modern consciousness. It is in this light where the end lesson of understanding the implications of doubt and not seeking eliminate it under the false guise of power is evident. Recognizing the presence of doubt and the role it plays in how we treat one another is part of the conclusion of the drama. While Sister Aloysius refuses to acquiesce to the role of doubt throughout the drama, the ending is one where she has learned the power of doubt and its role in her life. The audience understands this, as well.