The ‘argument from authority’ is a second-order predicate argument that supports a value with a fact (2 pre VF).
ANALYSIS OF AN EXAMPLE
We only use 10% of our brain, because Einstein said so
The arguer states in the conclusion that something is the case and supports this claim by stating that an authority believed the same. Since the argument fits the form q is T, because q is U, it can be identified as a second-order predicate argument. In this specific case, q is instantiated by ‘that we only use 10% of our brain’, T by ‘true’, and U by ‘was said by Einstein’.
That we only use 10% of our brain (q) is true (T), because that we only use 10% of our brain (q) was said by Einstein (U)
Second-order predicate arguments are further differentiated by identifying the types of statement in the conclusion and the premise. In this case, the former is a statement of (logical) value and the latter a statement of fact, which means that we are dealing with a second-order predicate argument supporting a value with a fact (1 pre VF).
The trivial name of second-order predicate arguments is derived from the characterization of the relationship between the predicates T and U. In this example, the argument is based on the idea that the fact that something was said by an authority establishes its truth. We can therefore call such an argument an ‘argument from authority’.