Falsification. An important point here is that if the prediction fails then the theory must be discarded or changed. If it was really his superior intelligence, then the prediction would be that the two friends would either agree that only his shadow had the aura, or perhaps they would see no aura at all (because of their inferior intelligence!). The simple observation that each sees his own aura falsifies his theory because not all three can have an intelligence superior to both the others.<quoted text>Depends..did it fail entirely or just part of it?
gracity is afailed theory , do you not believe in gravity?
which particular theories are you refering to?
These three steps are usually repeated over and over, often refining the theory after each set of new observations or experiments, with increasingly difficult testing hurdles for the theory to overcome. The most valuable theories are those which make precise and risky predictions, which could easily disprove the theory if they failed.