Quintilian, Institutio Oratoria, Book 7
Harold Edgeworth Butler, Ed.

[44] Again, there are questions concerned with numerical quantity which turn on a point of law, such as the questions whether thirty [p. 133] rewards are due to Thrasybulus,¹ or whether, when two thieves have stolen a sum of money, they are each to be required to refund fourfold or twofold. But in these cases, too, valuation of the act is necessary, and yet the point of law also turns on quality.

V. He who neither denies nor defends his act nor asserts that it was of a different nature from that alleged, must take his stand on some point of law that tells in his favour, a form of defence which generally turns on the legality of the action brought against him.