Isn't any backtested strategy that produces positive results based on a certain time series of past data, curve fitted? How does one avoid this? Whatever entry/exit parameters you use to trade - however "loose" and open ended you make them - (values for your momentum indicators, channels, volatility, etc. etc.) need certain values of input that will perform well in the past. Aren't all backtested strategies then, subject to hindsight bias? How does one determine that the past will repeat itself, in order for the selected trading parameters to continue to remain profitable in the future? Moreover, wouldn't other traders pick up on the repetition of the pattern (provided it continued in the future) and erode this so-called edge? Cheers.