Defining friction and asking what causes it might seem like a trivial question. Friction seems simple enough to understand. Friction is a force between surfaces that pushes against things that are moving or tending to move, and the rougher the surfaces, the greater the friction. Bill Robertson answers this by saying, "Well, not exactly". He then describes a few activities that could change a person's understanding of friction. He also explains his viewpoint on how friction was invented rather than discovered in the first place.