Earlier I wrote about theme as though it had to be a statement or opinion about life. Like much with writing, this is a rule made to be broken. If a theme can be a statement, can’t it also be a question? Absolutely!
I do believe that a theme says something about life. Every book poses one or more questions. An author can attempt to answer the question through their characters and plot or subplots. This is probably the most common choice. But sometimes an author will try to present two (or more) perspectives, give them equal weight, and then present a dilemma with no clear “all good” path forward.
Why would a writer choose this path? Maybe as a personal challenge – it is probably the more difficult and less used of the paths. But the decision might also come from what the author wants for the reader. I think that writers who choose to not answer the theme’s question are writers who want readers to really think about the book. By not giving the reader an easy out – by not giving them the answer – the question haunts the reader. The readers must devise their own answers.
Theme does not have to pose a question that either has a clear answer or no answer. I am sure that you can choose an approach that falls somewhere on the spectrum. An answer that is mostly good with some bad. An answer that blends the different perspectives. An answer that follows the “bad” perspective and leaves the readers dissatisfied (which means you have made your point). Okay, you get the picture. So all that is left is to decide how you want to present your question to your readers.