Quote from Cutten:
After all, trading is incredibly simple - there are only a handful of variables (price, time, volume, open interest), and you can only be long, flat, or short.
Also, the vast majority of system trading seems to be done by humans, Why can't a trading program, once written, scan the markets itself and then trade profitably?
A computer can be programmed to play chess because the elements of the chess-system are readily identifiable, and their possible dynamic relationships can be modelled (comprehended) by the computer's programmer.
A stock, commodity, or index, on the other hand, is a pseudo-system by way of being an epiphenomenal sub-system of the global economy and is, therefore, subject to myriad extra-systemic influences.
These external influences are not quantifiable; a program cannot be written to model the true system - the entire world.
