Oh, I agree completely with this. I think the novel, as a form, is perfect for it, really. It comes with a built-in irony from the outset. It’s great as a “laboratory” for ideas (or a playground).
Heck, you don’t even necessarily need characters. I love the “essayistic novels” (or novelistic essays, if you will) of a writer like Milan Kundera. Kundera has characters, sure, but also lengthy passages where ideas are explored in the narrator’s voice (or sort of shuffled between the characters and the narrator). Just by virtue of being in a novel, as opposed to an essay or pamphlet (or message board post), those ideas acquire a twinkle in their eye and a tongue-in-cheek sort of quality, a sense of “don’t take me completely seriously, I’m not being confrontational, I’m playing to see what happens”.
Another example of this that I like: The South African writer J. M. Coetzee has written a lot on the subject of animal rights. He’s a vegetarian and has frequently expressed clear opinions about the eating of animals and the meat industry. However, in his novella The Lives of Animals, these ideas are put into a fictionalized context, and presented as a lecture given by the fictional author Elizabeth Costello (a recurring character in Coetzee’s writings who is often seen as his “fictional alter ego”).
This re-framing completely changes the tone of the discussion. Instead of being polemic, it’s playful. Instead of being confrontational, it makes you think. (It also bugs the hell out of people like Peter Singer, since it means that Coetzee can follow his trains of thought without really committing to a position.)
Of course, I think Coetzee does this completely intentionally, as a way to explore ideas rather than argue them. (See? Now I’m talking about intentions. Hah! The irony.) Point is, it shows that if you want to be polemic, and convince someone of a point of view, the novel, as a form, is completely crap at it. It you want to invite someone to a discussion, start wheels turning in your readers’ heads, and have them think for themselves, it’s great.
Of course, this isn’t all that novels can do. They spend most of the time doing completely different things. But it is one thing that they can do, and do well. They should probably do more of it.