I like simple movies with a simple plot. I like simple acting, maybe even bordering to caricature. "Doubt" has that, but then, really not much more.
The plot is almost too meatless to carry the whole movie, if it were not for some serious acting. Meryl Streep really shines here as Sister Aloysius, throwing all of her acting abilities in the pot, as if told to go almost overboard in stereotypical, nun principal characterization. Hoffman does a decent job as father Flynn who basically seems to just be himself with no need to put much effort into it. Aloysius suspects he has an inappropriate relation with one of the altar boys. Adams is fine as the inexperienced and credulous sister James, who is the boy's history teacher.
There is a weak side story about Flynn's ability to come between the two sisters by convincing James, that he is innocent by manipulating her, but it does not really flesh out in any interesting way. Then there is a side story about the boy's mother and father, which is unnecessary filling, to stretch the simple plot.
What carries this movie to the end credits, is Streeps characterization of Sister Aloysius. She actually looks like she has been a nun for many years and knows the tricks of the trade. She also gives the expression well, that she has experience from outside the "church" and that she is using that empathy, to guide her "detective" work. You also sense her inner battle of doubt about Flynn, since the evidence against him, is not that impressive. She even has to make up a lie to get him to expose himself. Solid acting by Streep, that you can enjoy all the way through, and that is pretty much it
Rating: 6/10