This can be thought of as an extension of the post, "Ohm's Law and its Validity" but not necessarily so, since the train of thought which led me to this was not the same.

When someone makes a prediction or a prophecy, the system changes. The system with the prophecy is not necessarily the system without the prophecy. The nature of the system has changed. You ask how? When one hears a prophecy about oneself, one tries to either avoid it or fulfil it based on whether or not it is favourable to oneself. Therefore, the person who has heard the prophecy is different from the one who has not. Oft one meets his destiny on the road he takes to avoid it. Whatever the brain seeks, it will find. Remember Kung Fu Panda? Remember Macbeth?

Thus prophecies, forecasts and predictions, like measurements, are only self-fulfilling and are not pictures of "the real truth"… And for that matter, is there a "real truth"?