What themes are in The Cider House Rules, and please explain?

There are many themes. I will unpack what I think is the major theme.

There is the theme of abortion. However, this theme is argued from both sides, which makes the movie nuanced and a good one. On the one hand, the movie portrays abortion from a positive angle by portraying what happens when it is outlawed. In short, women resort to illegal ones that are dangerous. Also it also explore a possible area where abortion might be considered acceptable by many people - incest.

On the other hand, this movie is also about orphans who were not aborted. They have a right to live and enjoy life. In the end, there is no one answer.