Hi Paul,
No doubt there are many variables that affect any movement of anything in the universe; I would agree with you. I would like to point out that you have narrowed your feedback mechanisms enormously by insisting on price movements as the only source of information about the state of the world.
What if you write in your diary: "Had interview with CEO of XYZ company and he assured me that they would not invest more capital in Brazil; but I think he is lying to me. I would expect them to have to sink more capital into Brazil to shore up their operations there within the next six months"? And then, lo and behold, the company invests more capital in Brazil in a years time despite the absolutist statement that they would not do such a thing. Whether there is a price movement or not, this is feedback on your ability to understand information.
Your comments are insisting on a success measurement that I am writing about as incomplete: returns. So at the outset we have a disagreement in denominator. Yes, returns are important as an outcome of choice, and hence a source of information; but certainly no the only source of information. That's all I am saying.
Wouldn't you like to be evaluating all of your choices, not just those that are captured by returns? I think the primary job of an investor is to understand information. Only if you are doing that well can you then be wise, intelligent, and decisive in your decision making: to buy, or not to buy. So my preferred source of evaluation is: To what degree is your consciousness in accord with reality?
Hope that helps to clarify my point of view.
With smiles,
Jason