What's this disorder called?

The disorder I'm thinking of causes its patient to believe something to be true because he says it.

I believe this disorder to be similar to, but distinguishable from, the God Complex. It may even be compatible with the God Complex.

With GC, a person refuses to accept that he was in error, or had failed something, despite overwhelming, irrefutable evidence. However, how he ever came to that belief in the first place is irrelevant to GC; what matters, as far as GC is concerned, is your dogged refusal to abandon the claim once you've reached it.

The disorder I'm thinking of, however, focuses more on how you come to accept a factoid as truth, rather than how you handle rebuttal evidence.

-Something wasn't true five minutes ago.
-You claim it.
-Then, your claim, alone, without more, automatically and instantly makes it suddenly become absolute, irrefutable, scientific fact, in the complete absense of extrinsic evidence. Your claim IS the evidence.

This mental disorder was exhibited by the bad guys in George Orwell's "Nineteen Eighty-Four."

‘On the contrary,’ he said, ‘YOU have not controlled it. That is what has brought you here. You are here because you have failed in humility, in self-discipline. You would not make the act of submission which is the price of sanity. You preferred to be a lunatic, a minority of one. Only the disciplined mind can see reality, Winston. You believe that reality is something objective, external, existing in its own right. You also believe that the nature of reality is self-evident. When you delude yourself into thinking that you see something, you assume that everyone else sees the same thing as you. But I tell you, Winston, that reality is not external. Reality exists in the human mind, and nowhere else. Not in the individual mind, which can make mistakes, and in any case soon perishes: only in the mind of the Party, which is collective and immortal. Whatever the Party holds to be the truth, is truth. It is impossible to see reality except by looking through the eyes of the Party. That is the fact that you have got to relearn, Winston. It needs an act of self-destruction, an effort of the will. You must humble yourself before you can become sane.'

O’Brien held up his left hand, its back towards Winston, with the thumb hidden and the four fingers extended.
‘How many fingers am I holding up, Winston?’
‘Four.’
‘And if the party says that it is not four but five—then how many?’
‘Four.’
The word ended in a gasp of pain. The needle of the dial had shot up to fifty-five. The sweat had sprung out all over Winston’s body. The air tore into his lungs and issued again in deep groans which even by clenching his teeth he could not stop. O’Brien watched him, the four fingers still extended. He drew back the lever. This time the pain was only slightly eased.
‘How many fingers, Winston?’
‘Four.’
The needle went up to sixty.
‘How many fingers, Winston?’
‘Four! Four! What else can I say? Four!’
The needle must have risen again, but he did not look at it. The heavy, stern face and the four fingers filled his vision. The fingers stood up before his eyes like pillars, enormous, blurry, and seeming to vibrate, but unmistakably four.
‘How many fingers, Winston?
‘Four! Stop it, stop it! How can you go on? Four! Four!’
‘How many fingers, Winston?’
‘Five! Five! Five!’
‘No, Winston, that is no use. You are lying. You still think there are four. How many fingers, please?’
‘Four! five! Four! Anything you like. Only stop it, stop the pain!’

"We control matter because we control the mind. Reality is inside the skull. You will learn by degrees, Winston. There is nothing that we could not do. Invisibility, levitation — anything. I could float off this floor like a soap bubble if I wish to. I do not wish to, because the Party does not wish it. You must get rid of those nineteenth-century ideas about the laws of Nature. We make the laws of Nature."

If somebody had this belief abut themselves in the real world, what would it be called?

Hey there. I had a very similar delusion at one point (my diagnosis is bipolar 1 - a few different times my mania was so severe it caused delusions and even hallucinations.)

At one point I was walking the streets of Chicago at 3 am back to my place and I had this belief that I had been chosen to be God - I "realized" that the world is remade anew every so often, and I was the conduit for it to change. So, everything I walked past was just now being invented - it existed because I had seen it. My memories and life experience were now the basis for the world to continue on, rising like a Phoenix, ect, ect.

I've also had the experience of thinking my thoughts and words were magical - I could use my mastery of self hypnosis (lol) to make certain phrases into these spells that would grant me powers, ect.

I don't think there's a specific diagnosis for the belief that your words create reality. This would probably fall under the umbrella of a psychotic/delusional belief. Which makes sense. The actual content of the delusion is unimportant, (although the content and specifics of the belief tend to be of paramount importance to the person who is experiencing them.) These kinds of things have a lot in common, so it makes sense to treat them all generically as "psychosis"

Psychosis can exist all on its own, or it can be a feature of other disorders such as bipolar or schizophrenia. It can be intermittent and changing, or persistent and consistent for some people. Some people go through a limited number of episodes and do not relapse, while for others it becomes self-sustaining and a lifelong struggle.

I guess it all depends on exactly which portion of the brain and which neurotransmitters are compromised. Kind of like how there are lots of different illnesses that can give you a fever, but the characteristics and treatment of a high fever are universal.

Hope that helps.

Delusion.