Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Those, however, who are engaged in instructing the ignorant will find it useful at first to adopt a slightly less rigid method: the road will not be absolutely straight to begin with, but it will be more open and will provide easier going. I would have them therefore learn above all things
Hence arise those questions of legal action or competence. For there are some things, which, although not laudable in themselves, are yet permitted by law; witness the passage in the Twelve Tables authorising creditors to divide up a debtor's body amongst themselves, a law which is repudiated by public custom. There are also certain things which although equitable are prohibited by law; witness the restrictions placed on testamentary disposition. [*]( e.g. that the legal heir must receive at least a quarter of the property. )
The accuser likewise has four things which he must keep in mind: he must prove that something was done, that a particular act was done, that it was wrongly done, and that he brings his charge according to law. Thus every cause will turn on the same sorts of questions, though the parts of plaintiff and defendant will sometimes be interchanged: for instance in the case of a claim for a reward, it will be the plaintiffs task to show that what was done was right.