The appeal to authority may take several forms. As a statistical syllogism, it will have the following basic structure:
Most of what authority a has to say on subject matter S is correct. a says p about S. Therefore, p is correct.
The strength of this argument depends upon two factors:
1. The authority is a legitimate expert on the subject.
2. A consensus exists among legitimate experts on the matter under discussion.
These conditions may also simply be incorporated into the structure of the argument itself, in which case the form may look like this:
X holds that A is true
X is a legitimate expert on the subject. T
he consensus of experts agrees with X.
Therefore, there's a presumption that A is true.