When you buy a share, you are expressing a prediction, but your prediction affects the future to which it relates. In the financial markets, judgments about the value of an investment profoundly affect the actual value of that investment. In all human events, our thinking about the events we participate in has an impact on the course of those events. In all human mechanism that changes reality as you go along. I call this reflexivity.
Markets can be self-correcting.
Participants discover that events fail to correspond to their expectations, and they can correct the error in their thinking. That is why the market economy is better than central planning. Biased views and half-truths can validate themselves and reinforce the bias until it becomes unsustainable. The consequences can be catastrophic. The invisible hand does not necessarily work like a pendulum.