Markets are always changing. Trends end. Tendencies change. Patterns fade. Edges diminshes. All system traders and advanced discretionary traders come to the question of: Is this robust enough? Or as others may ask: Is this working? When you start thinking of robustness of anything you end up with a lot of questions to yourself: So... how do you deal with it? When you get a good backtested trading system, what do you do to confirm it is robust? When you optimize or use some sort of AI., what do you use as a fitness? What is robustness? How do you define it? Empirical... Quantitative... Risk Management? ... let's discuss about robustness.