technique - How to write a story that argues an idea

I apologize for the wording of my question; it's probably not very clear. I've got this idea for a book that explores a sort of philosophical theory. Similar to some of Ayn Rand's work (not her philosophies, but just the type of book itself). Other than how difficult it is to create characters for this, and settings, and a plot, I'm also concerned that I might not portray it correctly. I don't want to tell the reader outright what I want them to think. No "Thus we see…" I don't want them to feel like this is preaching. How do you create it so that it poses questions to the reader and makes them think and begin to see the argument? Say for example I want to write a book about how smoking is bad. I write a story where a kid's mom gets lung cancer and dies and he gets second hand smoking and gets emphysema. The message is pretty clear and people might hate because it's preachy. I don't want to do that.