Can a psychic claims his/her self-fulfilling prophecy as true, i.e. your knowledge of the prophecy makes you behave in a way that makes the prophecy comes true? An example: Your lover ask a fortuneteller about the future of your relationship. After consulting his/her tarot card (and probably conjuring a spell), the fortuneteller told your lover that your relationship will end in a summer. Your lover called you, telling his/her anxiety about this prophecy, and started to get overly paranoid. He/She start to interrogate your whereabouts all the time. Then, one hot summer day, stressed out by the strain of your relation with your overly-paranoid lover, you start to flirt the next hunky half naked men/scantily clad babe, find him/her interesting, and decide to end your relationship with your lover. The prophecy is fulfilled.
Can the fortune-teller takes credit for the accuracy of his/her prophecy? We might say that he/she has such clairvoyance to see the future, if we take the result at face value that is. However, the knowledge of the prophecy must also affect the prophecee (the guy who is prophecied. Is this a correct English word? Whatever) and he/she will behave accordingly in such a way that makes the prophecy comes true. There is a positive feedback between the prophecee’s belief and behaviour. In our example, the lover who learns from the prophet about the end of his/her relationship start to behave in way that cause the end of the relationship. If your lover didn’t know anything about the prophecy, then your lover would behave normally and will not stress you out. Your relationship will goes on well and in the end you might live happily ever after. The prophecy does not came out true then.
The good ‘ol Professor Wiki sums up this situation quite nicely:
A prophecy declared as truth when it is actually false may sufficiently influence people, either through fear or logical confusion, so that their reactions ultimately fulfill the once-false prophecy.
This is, I might say, a property inherent of a prophecy: It can be self-fulfilling if you allow it to interact with the subject of the prophecy. Borrowing terminologies from the physical sciences: The interaction between the prophecy and its subject can change the “trajectory” of the subject, thus aligning the subject with the “trajectory” of the prophecy.
Thus the only way to perform an experiment on the truthfulness of a prophecy is by performing a blind experiment: You can not tell the subject about what is going to happen, otherwise what should come out as false will come out as true, rendering the experiment moot. Thus as a prophet you should keep your prophecy to yourself (or anybody else other than the subject).
Consequently, there is no way whatsoever to prove to your subject the truth about your prophecy ex post facto (after the fact), because your subject must not know anything about your prophecy a priori and your subject does not know anything whatsoever about what you think will happen.
Thus we have a situation in which 1) the truth about prophecy can only be proven only by the prophet itself and there is no way he can convey it to the subject; 2) For the subject there is not much use in knowing the future because our interaction with the knowledge of the future can change the future anyway.