Learn English – word or phrase for someone whose ominous remarks come true

The biggest problem in finding a technical fallacy is that "absurd", in this context, isn't detailed enough. Why is it absurd? The idea that any absurd thing could be believed if it was simply absurd enough is not really true.

The idea of arguing something as true because no one would make it up is close to these fallacies:

• appeal to authority — using the speaker or source as evidence that it must be true
• proof by verbosity / proof by intimidation — using lots of variously connected evidence or jargon that overwhelms the listener such that it is easier to just assume that the proof is correct
• misleading vividness — using supreme detail in one example to form an incorrect generalization
• Big Lie

Strangely enough, the last is pretty darn close and is described as:

a lie so "colossal" that no one would believe that someone "could have the impudence to distort the truth so infamously."

If you notice the quotes in that quote, you may wonder who coined the term. It was Adolf Hilter in his book Mein Kampf. In a certain sense, this Big Lie is an appeal to authority mixed with a strong pull on assumed morality.

Many tend to think of an appeal to authority as the style of bringing in a football player to advertise footballs: Since the player uses football, surely he knows which are best. But appeal to authority also includes what we are talking about here. Trying to list the steps it would look something like this:

1. Idea
2. Idea appears absurd
3. The person claiming Idea couldn't/wouldn't lie/imagine such an absurd thing
4. Therefore it is not absurd
5. Therefore Idea is plausible/true

The 3-4 step is the appeal to authority. Using English, these are all appeals to authority:

Well, they couldn't possibly make something like that up

All of humanity isn't clever enough to think of something like that

Sam is a terrible liar; therefore this isn't a lie

In conclusion, most "so absurd it must be true" arguments are likely to include one of these somewhere. They probably have other problems, too, considering how absurd they are. The specific term Big Lie is appropriate for someone who actually created such an absurd argument and is using it against the people who consider it too absurd to doubt.

If you want to convey the idea of someone's who makes the final decision, whose word is respected and whose opinion is never disputed, consider the following options.

• He who must be obeyed. Better known as she who must be obeyed. Its meaning is self explanatory and in the OP's context this phrase might be said in all seriousness or in a lighter, more humorous tone of voice.
• He's the boss. Not exactly an idiom but it implies that you don't mess around with this person and whatever decision he makes is final. A related idiom is show somebody who's boss

We had had a special respect for my father in my family and his

opinions and ideas were always accepted by other family members and as they put it, he was the boss.

• His word is law. There's no use questioning any of his rules - his word is law around here.

• Say-so. Usually a permission or instruction to do something given by a figure of authority. Nothing happens without his say-so.

and as they put it, nothing was decided without his say-so

• Have the final say. In many families, the mother has the last say on the children's education and activities.

...We had had a special respect for my father in my family and his opinions and ideas were always accepted by other family members and as they put it, he had the final say.