Berger's sixth and final STEPPS principle is Stories. Narrative is the oldest and most powerful medium for transmitting information between people. We tell each other stories constantly: about what happened to us, about what we witnessed, about what we heard from someone else. Berger argues that ideas, products, and behaviours can ride inside stories the way viruses ride inside a host. When a story is compelling enough to be retold, anything embedded inside it gets transmitted with it. The critical design challenge is what Berger calls the Trojan Horse problem. A great story that has your brand message bolted on the side does not work: people tell the story and forget the brand. The message needs to be integral to the story, not decorative. If people cannot tell the story without mentioning the brand or the idea, the story carries the message every time it is told. Subway's Jared campaign worked not because it was an interesting weight-loss story, but because Subway was the mechanism. You could not tell the story without mentioning the product. Compare this to a clever advertising story that you enjoy but cannot remember what it was advertising: the story spread but the message did not. For communicators, the question is: can people tell the story without mentioning what I want them to remember? If yes, the story is a vehicle that loses its cargo.