Assigning any credibility to a statement based on the identity of its source is indeed the logical fallacy known as "appeal to authority". Whether you say "it

Assigning any credibility to a statement based on the identity of its source is indeed the logical fallacy known as "appeal to authority". Whether you say "it must be true", or "it is likely to be true" does not matter. Credibility must only come from the statement itself and the evidence to support it. However, while it is a logical fallacy, it is reasonable to temporarily hold beliefs for or against the truthfulness of a statement while no or insufficient evidence is present. As long as belief is not mistaken for proof, nothing is wrong about having such gut-feeling.