Or is there more there? Something you did or did not intend to be there.
Our minds are constantly working when we're writing. I often say my subconscious is smarter than I am. I've talked to a lot of writers who will look at their work long after they'd finished it and said 'how'd that get in there'? Also there's the almost comical way people will put their own interpretations on a work. You see this a lot in college.
Sometimes our readers can spot things that we can't, because we're too close to the work. And sometimes they're just filtering everything through their own world view. Which can make them embrace your stories for reasons unrelated to what you intend and it can make them reject it for the same reason.
But lets assume you decide to do this consciously. Theme gets talked about in a number of books on writing but that really boils down to 'what is your story about'? Even a straightforward man vs nature story of survival can be about more than just making it back to civilization. It can be 'about' discovering your limits aren't what you think they are. Or that survival at any cost means paying more than you intended. More complex plots may touch on the importance of faith in a carnal world. Or the madness of blind belief in...pick your poison: God, Leaders, Business, the American Dream.