Quintilian Institutio Oratoria 5.11.42

[42] Some include under this head the supernatural authority that is derived from oracles, as for instance the response asserting that Socrates was the wisest of mankind: indeed, they rank it above all other authorities. Such authority is rare, but may prove useful. It is employed by Cicero in his speech on the Replies of the Soothsayers ¹ and in the oration in which he denounced Catiline to the people, ² when he points to the statue of Jupiter crowning a column, and again in the pro Ligario, ³ where lie admits the cause of Caesar to be the better because the gods have decided in his favour. When such arguments are inherent in the case itself they are called supernatural evidence; when they are adduced from without they are styled supernatural arguments.