The argument from sign is a first-order predicate argument that supports a fact with another fact (1 pre FF).
ANALYSIS OF AN EXAMPLE
The suspect was driving fast, because he left a long trace of rubber on the road
The arguer states in the conclusion that someone was driving fast and supports this claim by stating that the same person left a long trace of rubber on the road. Since the argument fits the form a is X, because a is Y, it can be identified as a first-order predicate argument. In this specific case, a is instantiated by ‘the suspect’, X is instantiated by ‘was driving fast’, and Y is instantiated by ‘left a long trace of rubber on the road’.
The suspect (a) was driving fast (X), because the suspect (a) left a long trace of rubber on the road (Y)
First-order predicate arguments are further differentiated by identifying the types of statement in the conclusion and the premise. In this case, both are statements of fact, which means that we are dealing with a first-order predicate argument supporting a fact with a fact (1 pre FF).
The trivial name of first-order predicate arguments is derived from the characterization of the relationship between the predicates X and Y. In this example, the presence of the one fact, leaving a long trace of rubber on the road (Y), indicates the presence of the other fact, driving fast (X). We can therefore call such an argument an ‘argument from sign’.