“…It might be expected that very little can be said with this approach, but the model-free literature ( [18,6,20,8,13,19,22,21,23,3,15,1]) shows that if we take the prices of vanilla options as given, and only consider martingale models which are consistent with these prices, then we can find non-trivial bounds on the prices of exotic derivatives. In this literature the idea is to not specify a model, or even a probability space or filtration.…”