They get it using an "Argument of Authority" fallacy. This technique is used against us often. So and So says this is true, so it must be.

That is a logical fallacy.

Now that doesn't mean it may not be true. If the person really knows that subject then there is a higher probability of it being true, yet there is also a slim chance that it is not.

So a wise person will still listen to experts and make decisions based upon probabilities. Yet there is no MUST be true due to the authority of a person or persons. There is a HIGHLY LIKELY to be true in many cases. Or TRUE as far as we currently know. :)