Institutio Oratoria

Does not the orator discuss the question whether livid spots and swellings on the body are symptomatic of ill-health or poison? And yet that is a question for the qualified physician. Will he not deal with measurements and figures? And yet we must admit that they form part of mathematics. For my part I hold that practically all subjects are under certain circumstances liable to come up for treatment by the orator. If the circumstances do not occur, the subjects will not concern him.

We were therefore right in asserting that the material of rhetoric is composed of everything that comes before the orator for treatment, an assertion which is confirmed by the practice of everyday speech. For when we have been given a subject on which to speak, we often preface our remarks by calling attention to the fact that the matter has been laid before us.

Gorgias indeed felt so strongly that it was the orator's duty to speak on every subject, that he used to allow those who attended his lectures to ask him questions on any subject they pleased. Hermagoras also asserted that the material of oratory lay in the cause and the questions it involved, thereby including every subject that can be brought before it.